Merge ref 'b56aaec52b' from rust-lang/rust

Pull recent changes from https://github.com/rust-lang/rust via Josh.

Upstream ref: b56aaec52b
Filtered ref: 12f5e3255df658296af9fc953d8c1ab79ba91ea3

This merge was created using https://github.com/rust-lang/josh-sync.

.github/workflows/spellcheck.yml

@@ -1,23 +0,0 @@
-# This workflow runs spellcheck job
-
-name: Spellcheck
-on:
-  pull_request:
-    branches:
-      - "**"
-
-jobs:
-  spellcheck:
-    name: run spellchecker
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout the source code
-        uses: actions/checkout@v4
-
-      - name: check typos
-        # sync version with src/tools/tidy/src/ext_tool_checks.rs in spellcheck_runner
-        uses: crate-ci/typos@v1.34.0
-        with:
-          # sync target files with src/tools/tidy/src/ext_tool_checks.rs in check_impl
-          files: ./compiler ./library ./src/bootstrap ./src/librustdoc
-          config: ./typos.toml

.gitignore

@@ -85,8 +85,6 @@ __pycache__/
 
 ## Node
 node_modules
-package-lock.json
-package.json
 /src/doc/rustc-dev-guide/mermaid.min.js
 
 ## Rustdoc GUI tests

Cargo.lock

@@ -4563,7 +4563,10 @@ dependencies = [
  "rustc_macros",
  "rustc_serialize",
  "rustc_span",
+ "serde",
+ "serde_derive",
  "serde_json",
+ "serde_path_to_error",
  "tracing",
 ]
 
@@ -4955,6 +4958,16 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "serde_path_to_error"
+version = "0.1.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "59fab13f937fa393d08645bf3a84bdfe86e296747b506ada67bb15f10f218b2a"
+dependencies = [
+ "itoa",
+ "serde",
+]
+
 [[package]]
 name = "serde_spanned"
 version = "0.6.9"

REUSE.toml

@@ -37,6 +37,8 @@ path = [
     "rust-bors.toml",
     "triagebot.toml",
     "typos.toml",
+    "package.json",
+    "package-lock.json",
     "x",
     "x.ps1",
     "x.py",

compiler/rustc_abi/src/layout.rs

@@ -313,7 +313,6 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
         scalar_valid_range: (Bound<u128>, Bound<u128>),
         discr_range_of_repr: impl Fn(i128, i128) -> (Integer, bool),
         discriminants: impl Iterator<Item = (VariantIdx, i128)>,
-        dont_niche_optimize_enum: bool,
         always_sized: bool,
     ) -> LayoutCalculatorResult<FieldIdx, VariantIdx, F> {
         let (present_first, present_second) = {
@@ -352,13 +351,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             // structs. (We have also handled univariant enums
             // that allow representation optimization.)
             assert!(is_enum);
-            self.layout_of_enum(
-                repr,
-                variants,
-                discr_range_of_repr,
-                discriminants,
-                dont_niche_optimize_enum,
-            )
+            self.layout_of_enum(repr, variants, discr_range_of_repr, discriminants)
         }
     }
 
@@ -599,7 +592,6 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
         variants: &IndexSlice<VariantIdx, IndexVec<FieldIdx, F>>,
         discr_range_of_repr: impl Fn(i128, i128) -> (Integer, bool),
         discriminants: impl Iterator<Item = (VariantIdx, i128)>,
-        dont_niche_optimize_enum: bool,
     ) -> LayoutCalculatorResult<FieldIdx, VariantIdx, F> {
         // Until we've decided whether to use the tagged or
         // niche filling LayoutData, we don't want to intern the
@@ -618,7 +610,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
         }
 
         let calculate_niche_filling_layout = || -> Option<TmpLayout<FieldIdx, VariantIdx>> {
-            if dont_niche_optimize_enum {
+            if repr.inhibit_enum_layout_opt() {
                 return None;
             }
 

compiler/rustc_abi/src/lib.rs

@@ -1376,6 +1376,28 @@ impl WrappingRange {
         }
     }
 
+    /// Returns `true` if all the values in `other` are contained in this range,
+    /// when the values are considered as having width `size`.
+    #[inline(always)]
+    pub fn contains_range(&self, other: Self, size: Size) -> bool {
+        if self.is_full_for(size) {
+            true
+        } else {
+            let trunc = |x| size.truncate(x);
+
+            let delta = self.start;
+            let max = trunc(self.end.wrapping_sub(delta));
+
+            let other_start = trunc(other.start.wrapping_sub(delta));
+            let other_end = trunc(other.end.wrapping_sub(delta));
+
+            // Having shifted both input ranges by `delta`, now we only need to check
+            // whether `0..=max` contains `other_start..=other_end`, which can only
+            // happen if the other doesn't wrap since `self` isn't everything.
+            (other_start <= other_end) && (other_end <= max)
+        }
+    }
+
     /// Returns `self` with replaced `start`
     #[inline(always)]
     fn with_start(mut self, start: u128) -> Self {

compiler/rustc_abi/src/tests.rs

@@ -5,3 +5,66 @@ fn align_constants() {
     assert_eq!(Align::ONE, Align::from_bytes(1).unwrap());
     assert_eq!(Align::EIGHT, Align::from_bytes(8).unwrap());
 }
+
+#[test]
+fn wrapping_range_contains_range() {
+    let size16 = Size::from_bytes(16);
+
+    let a = WrappingRange { start: 10, end: 20 };
+    assert!(a.contains_range(a, size16));
+    assert!(a.contains_range(WrappingRange { start: 11, end: 19 }, size16));
+    assert!(a.contains_range(WrappingRange { start: 10, end: 10 }, size16));
+    assert!(a.contains_range(WrappingRange { start: 20, end: 20 }, size16));
+    assert!(!a.contains_range(WrappingRange { start: 10, end: 21 }, size16));
+    assert!(!a.contains_range(WrappingRange { start: 9, end: 20 }, size16));
+    assert!(!a.contains_range(WrappingRange { start: 4, end: 6 }, size16));
+    assert!(!a.contains_range(WrappingRange { start: 24, end: 26 }, size16));
+
+    assert!(!a.contains_range(WrappingRange { start: 16, end: 14 }, size16));
+
+    let b = WrappingRange { start: 20, end: 10 };
+    assert!(b.contains_range(b, size16));
+    assert!(b.contains_range(WrappingRange { start: 20, end: 20 }, size16));
+    assert!(b.contains_range(WrappingRange { start: 10, end: 10 }, size16));
+    assert!(b.contains_range(WrappingRange { start: 0, end: 10 }, size16));
+    assert!(b.contains_range(WrappingRange { start: 20, end: 30 }, size16));
+    assert!(b.contains_range(WrappingRange { start: 20, end: 9 }, size16));
+    assert!(b.contains_range(WrappingRange { start: 21, end: 10 }, size16));
+    assert!(b.contains_range(WrappingRange { start: 999, end: 9999 }, size16));
+    assert!(b.contains_range(WrappingRange { start: 999, end: 9 }, size16));
+    assert!(!b.contains_range(WrappingRange { start: 19, end: 19 }, size16));
+    assert!(!b.contains_range(WrappingRange { start: 11, end: 11 }, size16));
+    assert!(!b.contains_range(WrappingRange { start: 19, end: 11 }, size16));
+    assert!(!b.contains_range(WrappingRange { start: 11, end: 19 }, size16));
+
+    let f = WrappingRange { start: 0, end: u128::MAX };
+    assert!(f.contains_range(WrappingRange { start: 10, end: 20 }, size16));
+    assert!(f.contains_range(WrappingRange { start: 20, end: 10 }, size16));
+
+    let g = WrappingRange { start: 2, end: 1 };
+    assert!(g.contains_range(WrappingRange { start: 10, end: 20 }, size16));
+    assert!(g.contains_range(WrappingRange { start: 20, end: 10 }, size16));
+
+    let size1 = Size::from_bytes(1);
+    let u8r = WrappingRange { start: 0, end: 255 };
+    let i8r = WrappingRange { start: 128, end: 127 };
+    assert!(u8r.contains_range(i8r, size1));
+    assert!(i8r.contains_range(u8r, size1));
+    assert!(!u8r.contains_range(i8r, size16));
+    assert!(i8r.contains_range(u8r, size16));
+
+    let boolr = WrappingRange { start: 0, end: 1 };
+    assert!(u8r.contains_range(boolr, size1));
+    assert!(i8r.contains_range(boolr, size1));
+    assert!(!boolr.contains_range(u8r, size1));
+    assert!(!boolr.contains_range(i8r, size1));
+
+    let cmpr = WrappingRange { start: 255, end: 1 };
+    assert!(u8r.contains_range(cmpr, size1));
+    assert!(i8r.contains_range(cmpr, size1));
+    assert!(!cmpr.contains_range(u8r, size1));
+    assert!(!cmpr.contains_range(i8r, size1));
+
+    assert!(!boolr.contains_range(cmpr, size1));
+    assert!(cmpr.contains_range(boolr, size1));
+}

compiler/rustc_ast/src/format.rs

@@ -1,5 +1,5 @@
 use rustc_data_structures::fx::FxHashMap;
-use rustc_macros::{Decodable, Encodable};
+use rustc_macros::{Decodable, Encodable, Walkable};
 use rustc_span::{Ident, Span, Symbol};
 
 use crate::Expr;
@@ -41,7 +41,7 @@ use crate::token::LitKind;
 /// Basically the "AST" for a complete `format_args!()`.
 ///
 /// E.g., `format_args!("hello {name}");`.
-#[derive(Clone, Encodable, Decodable, Debug)]
+#[derive(Clone, Encodable, Decodable, Debug, Walkable)]
 pub struct FormatArgs {
     pub span: Span,
     pub template: Vec<FormatArgsPiece>,
@@ -63,7 +63,7 @@ pub struct FormatArgs {
 /// A piece of a format template string.
 ///
 /// E.g. "hello" or "{name}".
-#[derive(Clone, Encodable, Decodable, Debug)]
+#[derive(Clone, Encodable, Decodable, Debug, Walkable)]
 pub enum FormatArgsPiece {
     Literal(Symbol),
     Placeholder(FormatPlaceholder),
@@ -73,7 +73,7 @@ pub enum FormatArgsPiece {
 ///
 /// E.g. `1, 2, name="ferris", n=3`,
 /// but also implicit captured arguments like `x` in `format_args!("{x}")`.
-#[derive(Clone, Encodable, Decodable, Debug)]
+#[derive(Clone, Encodable, Decodable, Debug, Walkable)]
 pub struct FormatArguments {
     arguments: Vec<FormatArgument>,
     num_unnamed_args: usize,
@@ -144,13 +144,13 @@ impl FormatArguments {
     }
 }
 
-#[derive(Clone, Encodable, Decodable, Debug)]
+#[derive(Clone, Encodable, Decodable, Debug, Walkable)]
 pub struct FormatArgument {
     pub kind: FormatArgumentKind,
     pub expr: P<Expr>,
 }
 
-#[derive(Clone, Encodable, Decodable, Debug)]
+#[derive(Clone, Encodable, Decodable, Debug, Walkable)]
 pub enum FormatArgumentKind {
     /// `format_args(…, arg)`
     Normal,
@@ -170,24 +170,28 @@ impl FormatArgumentKind {
     }
 }
 
-#[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq)]
+#[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq, Walkable)]
 pub struct FormatPlaceholder {
     /// Index into [`FormatArgs::arguments`].
     pub argument: FormatArgPosition,
     /// The span inside the format string for the full `{…}` placeholder.
     pub span: Option<Span>,
     /// `{}`, `{:?}`, or `{:x}`, etc.
+    #[visitable(ignore)]
     pub format_trait: FormatTrait,
     /// `{}` or `{:.5}` or `{:-^20}`, etc.
+    #[visitable(ignore)]
     pub format_options: FormatOptions,
 }
 
-#[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq)]
+#[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq, Walkable)]
 pub struct FormatArgPosition {
     /// Which argument this position refers to (Ok),
     /// or would've referred to if it existed (Err).
+    #[visitable(ignore)]
     pub index: Result<usize, usize>,
     /// What kind of position this is. See [`FormatArgPositionKind`].
+    #[visitable(ignore)]
     pub kind: FormatArgPositionKind,
     /// The span of the name or number.
     pub span: Option<Span>,

compiler/rustc_ast/src/mut_visit.rs

@@ -12,14 +12,14 @@ use std::panic;
 
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
 use rustc_span::source_map::Spanned;
-use rustc_span::{Ident, Span};
+use rustc_span::{Ident, Span, Symbol};
 use smallvec::{SmallVec, smallvec};
 use thin_vec::ThinVec;
 
 use crate::ast::*;
 use crate::ptr::P;
 use crate::tokenstream::*;
-use crate::visit::{AssocCtxt, BoundKind, FnCtxt, VisitorResult, try_visit, visit_opt, walk_list};
+use crate::visit::{AssocCtxt, BoundKind, FnCtxt, LifetimeCtxt, VisitorResult, try_visit};
 
 mod sealed {
     use rustc_ast_ir::visit::VisitorResult;
@@ -36,11 +36,249 @@ mod sealed {
 
 use sealed::MutVisitorResult;
 
+pub(crate) trait MutVisitable<V: MutVisitor> {
+    type Extra: Copy;
+    fn visit_mut(&mut self, visitor: &mut V, extra: Self::Extra);
+}
+
+impl<V: MutVisitor, T: ?Sized> MutVisitable<V> for P<T>
+where
+    T: MutVisitable<V>,
+{
+    type Extra = T::Extra;
+    fn visit_mut(&mut self, visitor: &mut V, extra: Self::Extra) {
+        (**self).visit_mut(visitor, extra)
+    }
+}
+
+impl<V: MutVisitor, T> MutVisitable<V> for Option<T>
+where
+    T: MutVisitable<V>,
+{
+    type Extra = T::Extra;
+    fn visit_mut(&mut self, visitor: &mut V, extra: Self::Extra) {
+        if let Some(this) = self {
+            this.visit_mut(visitor, extra)
+        }
+    }
+}
+
+impl<V: MutVisitor, T> MutVisitable<V> for Spanned<T>
+where
+    T: MutVisitable<V>,
+{
+    type Extra = T::Extra;
+    fn visit_mut(&mut self, visitor: &mut V, extra: Self::Extra) {
+        let Spanned { span, node } = self;
+        span.visit_mut(visitor, ());
+        node.visit_mut(visitor, extra);
+    }
+}
+
+impl<V: MutVisitor, T> MutVisitable<V> for [T]
+where
+    T: MutVisitable<V>,
+{
+    type Extra = T::Extra;
+    fn visit_mut(&mut self, visitor: &mut V, extra: Self::Extra) {
+        for item in self {
+            item.visit_mut(visitor, extra);
+        }
+    }
+}
+
+impl<V: MutVisitor, T> MutVisitable<V> for Vec<T>
+where
+    T: MutVisitable<V>,
+{
+    type Extra = T::Extra;
+    fn visit_mut(&mut self, visitor: &mut V, extra: Self::Extra) {
+        for item in self {
+            item.visit_mut(visitor, extra);
+        }
+    }
+}
+
+impl<V: MutVisitor, T> MutVisitable<V> for (T,)
+where
+    T: MutVisitable<V>,
+{
+    type Extra = T::Extra;
+    fn visit_mut(&mut self, visitor: &mut V, extra: Self::Extra) {
+        self.0.visit_mut(visitor, extra);
+    }
+}
+
+impl<V: MutVisitor, T1, T2> MutVisitable<V> for (T1, T2)
+where
+    T1: MutVisitable<V, Extra = ()>,
+    T2: MutVisitable<V, Extra = ()>,
+{
+    type Extra = ();
+    fn visit_mut(&mut self, visitor: &mut V, extra: Self::Extra) {
+        self.0.visit_mut(visitor, extra);
+        self.1.visit_mut(visitor, extra);
+    }
+}
+
+impl<V: MutVisitor, T1, T2, T3> MutVisitable<V> for (T1, T2, T3)
+where
+    T1: MutVisitable<V, Extra = ()>,
+    T2: MutVisitable<V, Extra = ()>,
+    T3: MutVisitable<V, Extra = ()>,
+{
+    type Extra = ();
+    fn visit_mut(&mut self, visitor: &mut V, extra: Self::Extra) {
+        self.0.visit_mut(visitor, extra);
+        self.1.visit_mut(visitor, extra);
+        self.2.visit_mut(visitor, extra);
+    }
+}
+
+impl<V: MutVisitor, T1, T2, T3, T4> MutVisitable<V> for (T1, T2, T3, T4)
+where
+    T1: MutVisitable<V, Extra = ()>,
+    T2: MutVisitable<V, Extra = ()>,
+    T3: MutVisitable<V, Extra = ()>,
+    T4: MutVisitable<V, Extra = ()>,
+{
+    type Extra = ();
+    fn visit_mut(&mut self, visitor: &mut V, extra: Self::Extra) {
+        self.0.visit_mut(visitor, extra);
+        self.1.visit_mut(visitor, extra);
+        self.2.visit_mut(visitor, extra);
+        self.3.visit_mut(visitor, extra);
+    }
+}
+
+pub trait MutWalkable<V: MutVisitor> {
+    fn walk_mut(&mut self, visitor: &mut V);
+}
+
+macro_rules! visit_visitable {
+    (mut $visitor:expr, $($expr:expr),* $(,)?) => {{
+        $(MutVisitable::visit_mut($expr, $visitor, ());)*
+    }};
+}
+
+macro_rules! visit_visitable_with {
+    (mut $visitor:expr, $expr:expr, $extra:expr $(,)?) => {
+        MutVisitable::visit_mut($expr, $visitor, $extra)
+    };
+}
+
+macro_rules! walk_walkable {
+    ($visitor:expr, $expr:expr, mut) => {
+        MutWalkable::walk_mut($expr, $visitor)
+    };
+}
+
+macro_rules! impl_visitable {
+    (|&mut $self:ident: $self_ty:ty,
+      $vis:ident: &mut $vis_ty:ident,
+      $extra:ident: $extra_ty:ty| $block:block) => {
+        #[allow(unused_parens, non_local_definitions)]
+        impl<$vis_ty: MutVisitor> MutVisitable<$vis_ty> for $self_ty {
+            type Extra = $extra_ty;
+            fn visit_mut(&mut $self, $vis: &mut $vis_ty, $extra: Self::Extra) -> V::Result {
+                $block
+            }
+        }
+    };
+}
+
+macro_rules! impl_walkable {
+    ($(<$K:ident: $Kb:ident>)? |&mut $self:ident: $self_ty:ty,
+      $vis:ident: &mut $vis_ty:ident| $block:block) => {
+        #[allow(unused_parens, non_local_definitions)]
+        impl<$($K: $Kb,)? $vis_ty: MutVisitor> MutWalkable<$vis_ty> for $self_ty {
+            fn walk_mut(&mut $self, $vis: &mut $vis_ty) -> V::Result {
+                $block
+            }
+        }
+    };
+}
+
+macro_rules! impl_visitable_noop {
+    (<mut> $($ty:ty,)*) => {
+        $(
+            impl_visitable!(|&mut self: $ty, _vis: &mut V, _extra: ()| {});
+        )*
+    };
+}
+
+macro_rules! impl_visitable_list {
+    (<mut> $($ty:ty,)*) => {
+        $(impl<V: MutVisitor, T> MutVisitable<V> for $ty
+        where
+            for<'a> &'a mut $ty: IntoIterator<Item = &'a mut T>,
+            T: MutVisitable<V>,
+        {
+            type Extra = <T as MutVisitable<V>>::Extra;
+
+            #[inline]
+            fn visit_mut(&mut self, visitor: &mut V, extra: Self::Extra) {
+                for i in self {
+                    i.visit_mut(visitor, extra);
+                }
+            }
+        })*
+    }
+}
+
+macro_rules! impl_visitable_direct {
+    (<mut> $($ty:ty,)*) => {
+        $(impl_visitable!(
+            |&mut self: $ty, visitor: &mut V, _extra: ()| {
+                MutWalkable::walk_mut(self, visitor)
+            }
+        );)*
+    }
+}
+
+macro_rules! impl_visitable_calling_walkable {
+    (<mut>
+        $( fn $method:ident($ty:ty $(, $extra_name:ident: $extra_ty:ty)?); )*
+    ) => {
+        $(fn $method(&mut self, node: &mut $ty $(, $extra_name:$extra_ty)?) {
+            impl_visitable!(|&mut self: $ty, visitor: &mut V, extra: ($($extra_ty)?)| {
+                let ($($extra_name)?) = extra;
+                visitor.$method(self $(, $extra_name)?);
+            });
+            walk_walkable!(self, node, mut)
+        })*
+    }
+}
+
+macro_rules! define_named_walk {
+    ((mut) $Visitor:ident
+        $( pub fn $method:ident($ty:ty); )*
+    ) => {
+        $(pub fn $method<V: $Visitor>(visitor: &mut V, node: &mut $ty) {
+            walk_walkable!(visitor, node, mut)
+        })*
+    };
+}
+
 super::common_visitor_and_walkers!((mut) MutVisitor);
 
 macro_rules! generate_flat_map_visitor_fns {
     ($($name:ident, $Ty:ty, $flat_map_fn:ident$(, $param:ident: $ParamTy:ty)*;)+) => {
         $(
+            #[allow(unused_parens)]
+            impl<V: MutVisitor> MutVisitable<V> for ThinVec<$Ty> {
+                type Extra = ($($ParamTy),*);
+
+                #[inline]
+                fn visit_mut(
+                    &mut self,
+                    visitor: &mut V,
+                    ($($param),*): Self::Extra,
+                ) -> V::Result {
+                    $name(visitor, self $(, $param)*)
+                }
+            }
+
             fn $name<V: MutVisitor>(
                 vis: &mut V,
                 values: &mut ThinVec<$Ty>,
@@ -78,15 +316,6 @@ pub fn walk_flat_map_pat_field<T: MutVisitor>(
     smallvec![fp]
 }
 
-fn visit_nested_use_tree<V: MutVisitor>(
-    vis: &mut V,
-    nested_tree: &mut UseTree,
-    nested_id: &mut NodeId,
-) {
-    vis.visit_id(nested_id);
-    vis.visit_use_tree(nested_tree);
-}
-
 macro_rules! generate_walk_flat_map_fns {
     ($($fn_name:ident($Ty:ty$(,$extra_name:ident: $ExtraTy:ty)*) => $visit_fn_name:ident;)+) => {$(
         pub fn $fn_name<V: MutVisitor>(vis: &mut V, mut value: $Ty$(,$extra_name: $ExtraTy)*) -> SmallVec<[$Ty; 1]> {
@@ -109,14 +338,6 @@ generate_walk_flat_map_fns! {
     walk_flat_map_assoc_item(P<AssocItem>, ctxt: AssocCtxt) => visit_assoc_item;
 }
 
-fn walk_ty_alias_where_clauses<T: MutVisitor>(vis: &mut T, tawcs: &mut TyAliasWhereClauses) {
-    let TyAliasWhereClauses { before, after, split: _ } = tawcs;
-    let TyAliasWhereClause { has_where_token: _, span: span_before } = before;
-    let TyAliasWhereClause { has_where_token: _, span: span_after } = after;
-    vis.visit_span(span_before);
-    vis.visit_span(span_after);
-}
-
 pub fn walk_filter_map_expr<T: MutVisitor>(vis: &mut T, mut e: P<Expr>) -> Option<P<Expr>> {
     vis.visit_expr(&mut e);
     Some(e)

compiler/rustc_ast/src/tokenstream.rs

@@ -20,7 +20,7 @@ use std::{cmp, fmt, iter, mem};
 
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync;
-use rustc_macros::{Decodable, Encodable, HashStable_Generic};
+use rustc_macros::{Decodable, Encodable, HashStable_Generic, Walkable};
 use rustc_serialize::{Decodable, Encodable};
 use rustc_span::{DUMMY_SP, Span, SpanDecoder, SpanEncoder, Symbol, sym};
 use thin_vec::ThinVec;
@@ -977,7 +977,7 @@ impl TokenCursor {
     }
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)]
+#[derive(Debug, Copy, Clone, PartialEq, Encodable, Decodable, HashStable_Generic, Walkable)]
 pub struct DelimSpan {
     pub open: Span,
     pub close: Span,

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -157,6 +157,19 @@ pub enum UsedBy {
     Linker,
 }
 
+#[derive(Encodable, Decodable, Clone, Debug, PartialEq, Eq, Hash)]
+#[derive(HashStable_Generic, PrintAttribute)]
+pub enum MacroUseArgs {
+    UseAll,
+    UseSpecific(ThinVec<Ident>),
+}
+
+impl Default for MacroUseArgs {
+    fn default() -> Self {
+        Self::UseSpecific(ThinVec::new())
+    }
+}
+
 #[derive(Debug, Clone, Encodable, Decodable, HashStable_Generic)]
 pub struct StrippedCfgItem<ModId = DefId> {
     pub parent_module: ModId,
@@ -351,9 +364,15 @@ pub enum AttributeKind {
     /// Represents `#[loop_match]`.
     LoopMatch(Span),
 
+    /// Represents `#[macro_escape]`.
+    MacroEscape(Span),
+
     /// Represents `#[rustc_macro_transparency]`.
     MacroTransparency(Transparency),
 
+    /// Represents `#[macro_use]`.
+    MacroUse { span: Span, arguments: MacroUseArgs },
+
     /// Represents `#[marker]`.
     Marker(Span),
 

compiler/rustc_attr_data_structures/src/encode_cross_crate.rs

@@ -45,7 +45,9 @@ impl AttributeKind {
             LinkOrdinal { .. } => No,
             LinkSection { .. } => Yes, // Needed for rustdoc
             LoopMatch(..) => No,
+            MacroEscape(..) => No,
             MacroTransparency(..) => Yes,
+            MacroUse { .. } => No,
             Marker(..) => No,
             MayDangle(..) => No,
             MustUse { .. } => Yes,

compiler/rustc_attr_data_structures/src/lib.rs

@@ -24,7 +24,7 @@ use rustc_ast::token::CommentKind;
 use rustc_ast::{AttrStyle, IntTy, UintTy};
 use rustc_ast_pretty::pp::Printer;
 use rustc_span::hygiene::Transparency;
-use rustc_span::{ErrorGuaranteed, Span, Symbol};
+use rustc_span::{ErrorGuaranteed, Ident, Span, Symbol};
 pub use stability::*;
 use thin_vec::ThinVec;
 pub use version::*;
@@ -172,7 +172,7 @@ macro_rules! print_tup {
 print_tup!(A B C D E F G H);
 print_skip!(Span, (), ErrorGuaranteed);
 print_disp!(u16, bool, NonZero<u32>);
-print_debug!(Symbol, UintTy, IntTy, Align, AttrStyle, CommentKind, Transparency);
+print_debug!(Symbol, Ident, UintTy, IntTy, Align, AttrStyle, CommentKind, Transparency);
 
 /// Finds attributes in sequences of attributes by pattern matching.
 ///

compiler/rustc_attr_parsing/src/attributes/macro_attrs.rs

@@ -0,0 +1,115 @@
+use rustc_attr_data_structures::{AttributeKind, MacroUseArgs};
+use rustc_errors::DiagArgValue;
+use rustc_feature::{AttributeTemplate, template};
+use rustc_span::{Span, Symbol, sym};
+use thin_vec::ThinVec;
+
+use crate::attributes::{AcceptMapping, AttributeParser, NoArgsAttributeParser, OnDuplicate};
+use crate::context::{AcceptContext, FinalizeContext, Stage};
+use crate::parser::ArgParser;
+use crate::session_diagnostics;
+
+pub(crate) struct MacroEscapeParser;
+impl<S: Stage> NoArgsAttributeParser<S> for MacroEscapeParser {
+    const PATH: &[Symbol] = &[sym::macro_escape];
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Warn;
+    const CREATE: fn(Span) -> AttributeKind = AttributeKind::MacroEscape;
+}
+
+/// `#[macro_use]` attributes can either:
+/// - Use all macros from a crate, if provided without arguments
+/// - Use specific macros from a crate, if provided with arguments `#[macro_use(macro1, macro2)]`
+/// A warning should be provided if an use all is combined with specific uses, or if multiple use-alls are used.
+#[derive(Default)]
+pub(crate) struct MacroUseParser {
+    state: MacroUseArgs,
+
+    /// Spans of all `#[macro_use]` arguments with arguments, used for linting
+    uses_attr_spans: ThinVec<Span>,
+    /// If `state` is `UseSpecific`, stores the span of the first `#[macro_use]` argument, used as the span for this attribute
+    /// If `state` is `UseAll`, stores the span of the first `#[macro_use]` arguments without arguments
+    first_span: Option<Span>,
+}
+
+const MACRO_USE_TEMPLATE: AttributeTemplate = template!(Word, List: "name1, name2, ...");
+
+impl<S: Stage> AttributeParser<S> for MacroUseParser {
+    const ATTRIBUTES: AcceptMapping<Self, S> = &[(
+        &[sym::macro_use],
+        MACRO_USE_TEMPLATE,
+        |group: &mut Self, cx: &mut AcceptContext<'_, '_, S>, args| {
+            let span = cx.attr_span;
+            group.first_span.get_or_insert(span);
+            match args {
+                ArgParser::NoArgs => {
+                    match group.state {
+                        MacroUseArgs::UseAll => {
+                            let first_span = group.first_span.expect(
+                                "State is UseAll is some so this is not the first attribute",
+                            );
+                            // Since there is a `#[macro_use]` import already, give a warning
+                            cx.warn_unused_duplicate(first_span, span);
+                        }
+                        MacroUseArgs::UseSpecific(_) => {
+                            group.state = MacroUseArgs::UseAll;
+                            group.first_span = Some(span);
+                            // If there is a `#[macro_use]` attribute, warn on all `#[macro_use(...)]` attributes since everything is already imported
+                            for specific_use in group.uses_attr_spans.drain(..) {
+                                cx.warn_unused_duplicate(span, specific_use);
+                            }
+                        }
+                    }
+                }
+                ArgParser::List(list) => {
+                    if list.is_empty() {
+                        cx.warn_empty_attribute(list.span);
+                        return;
+                    }
+
+                    match &mut group.state {
+                        MacroUseArgs::UseAll => {
+                            let first_span = group.first_span.expect(
+                                "State is UseAll is some so this is not the first attribute",
+                            );
+                            cx.warn_unused_duplicate(first_span, span);
+                        }
+                        MacroUseArgs::UseSpecific(arguments) => {
+                            // Store here so if we encounter a `UseAll` later we can still lint this attribute
+                            group.uses_attr_spans.push(cx.attr_span);
+
+                            for item in list.mixed() {
+                                let Some(item) = item.meta_item() else {
+                                    cx.expected_identifier(item.span());
+                                    continue;
+                                };
+                                if let Err(err_span) = item.args().no_args() {
+                                    cx.expected_no_args(err_span);
+                                    continue;
+                                }
+                                let Some(item) = item.path().word() else {
+                                    cx.expected_identifier(item.span());
+                                    continue;
+                                };
+                                arguments.push(item);
+                            }
+                        }
+                    }
+                }
+                ArgParser::NameValue(_) => {
+                    let suggestions = MACRO_USE_TEMPLATE.suggestions(false, sym::macro_use);
+                    cx.emit_err(session_diagnostics::IllFormedAttributeInputLint {
+                        num_suggestions: suggestions.len(),
+                        suggestions: DiagArgValue::StrListSepByAnd(
+                            suggestions.into_iter().map(|s| format!("`{s}`").into()).collect(),
+                        ),
+                        span,
+                    });
+                }
+            }
+        },
+    )];
+
+    fn finalize(self, _cx: &FinalizeContext<'_, '_, S>) -> Option<AttributeKind> {
+        Some(AttributeKind::MacroUse { span: self.first_span?, arguments: self.state })
+    }
+}

compiler/rustc_attr_parsing/src/attributes/mod.rs

@@ -36,6 +36,7 @@ pub(crate) mod inline;
 pub(crate) mod link_attrs;
 pub(crate) mod lint_helpers;
 pub(crate) mod loop_match;
+pub(crate) mod macro_attrs;
 pub(crate) mod must_use;
 pub(crate) mod no_implicit_prelude;
 pub(crate) mod non_exhaustive;

compiler/rustc_attr_parsing/src/attributes/must_use.rs

@@ -34,7 +34,7 @@ impl<S: Stage> SingleAttributeParser<S> for MustUseParser {
                 ArgParser::List(_) => {
                     let suggestions =
                         <Self as SingleAttributeParser<S>>::TEMPLATE.suggestions(false, "must_use");
-                    cx.emit_err(session_diagnostics::MustUseIllFormedAttributeInput {
+                    cx.emit_err(session_diagnostics::IllFormedAttributeInputLint {
                         num_suggestions: suggestions.len(),
                         suggestions: DiagArgValue::StrListSepByAnd(
                             suggestions.into_iter().map(|s| format!("`{s}`").into()).collect(),

compiler/rustc_attr_parsing/src/attributes/stability.rs

@@ -74,8 +74,15 @@ impl<S: Stage> AttributeParser<S> for StabilityParser {
             template!(NameValueStr: "deprecation message"),
             |this, cx, args| {
                 reject_outside_std!(cx);
-                this.allowed_through_unstable_modules =
-                    args.name_value().and_then(|i| i.value_as_str())
+                let Some(nv) = args.name_value() else {
+                    cx.expected_name_value(cx.attr_span, None);
+                    return;
+                };
+                let Some(value_str) = nv.value_as_str() else {
+                    cx.expected_string_literal(nv.value_span, Some(nv.value_as_lit()));
+                    return;
+                };
+                this.allowed_through_unstable_modules = Some(value_str);
             },
         ),
     ];
@@ -247,7 +254,12 @@ pub(crate) fn parse_stability<S: Stage>(
     let mut feature = None;
     let mut since = None;
 
-    for param in args.list()?.mixed() {
+    let ArgParser::List(list) = args else {
+        cx.expected_list(cx.attr_span);
+        return None;
+    };
+
+    for param in list.mixed() {
         let param_span = param.span();
         let Some(param) = param.meta_item() else {
             cx.emit_err(session_diagnostics::UnsupportedLiteral {
@@ -322,7 +334,13 @@ pub(crate) fn parse_unstability<S: Stage>(
     let mut is_soft = false;
     let mut implied_by = None;
     let mut old_name = None;
-    for param in args.list()?.mixed() {
+
+    let ArgParser::List(list) = args else {
+        cx.expected_list(cx.attr_span);
+        return None;
+    };
+
+    for param in list.mixed() {
         let Some(param) = param.meta_item() else {
             cx.emit_err(session_diagnostics::UnsupportedLiteral {
                 span: param.span(),

compiler/rustc_attr_parsing/src/context.rs

@@ -33,6 +33,7 @@ use crate::attributes::lint_helpers::{
     AsPtrParser, AutomaticallyDerivedParser, PassByValueParser, PubTransparentParser,
 };
 use crate::attributes::loop_match::{ConstContinueParser, LoopMatchParser};
+use crate::attributes::macro_attrs::{MacroEscapeParser, MacroUseParser};
 use crate::attributes::must_use::MustUseParser;
 use crate::attributes::no_implicit_prelude::NoImplicitPreludeParser;
 use crate::attributes::non_exhaustive::NonExhaustiveParser;
@@ -126,6 +127,7 @@ attribute_parsers!(
         BodyStabilityParser,
         ConfusablesParser,
         ConstStabilityParser,
+        MacroUseParser,
         NakedParser,
         StabilityParser,
         UsedParser,
@@ -174,6 +176,7 @@ attribute_parsers!(
         Single<WithoutArgs<FfiPureParser>>,
         Single<WithoutArgs<FundamentalParser>>,
         Single<WithoutArgs<LoopMatchParser>>,
+        Single<WithoutArgs<MacroEscapeParser>>,
         Single<WithoutArgs<MarkerParser>>,
         Single<WithoutArgs<MayDangleParser>>,
         Single<WithoutArgs<NoImplicitPreludeParser>>,
@@ -386,6 +389,17 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
         })
     }
 
+    /// emit an error that a `name` was expected here
+    pub(crate) fn expected_identifier(&self, span: Span) -> ErrorGuaranteed {
+        self.emit_err(AttributeParseError {
+            span,
+            attr_span: self.attr_span,
+            template: self.template.clone(),
+            attribute: self.attr_path.clone(),
+            reason: AttributeParseErrorReason::ExpectedIdentifier,
+        })
+    }
+
     /// emit an error that a `name = value` pair was expected at this span. The symbol can be given for
     /// a nicer error message talking about the specific name that was found lacking a value.
     pub(crate) fn expected_name_value(&self, span: Span, name: Option<Symbol>) -> ErrorGuaranteed {

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -438,7 +438,7 @@ pub(crate) struct IllFormedAttributeInput {
 
 #[derive(Diagnostic)]
 #[diag(attr_parsing_ill_formed_attribute_input)]
-pub(crate) struct MustUseIllFormedAttributeInput {
+pub(crate) struct IllFormedAttributeInputLint {
     #[primary_span]
     pub span: Span,
     pub num_suggestions: usize,
@@ -549,6 +549,7 @@ pub(crate) enum AttributeParseErrorReason {
         /// Should we tell the user to write a list when they didn't?
         list: bool,
     },
+    ExpectedIdentifier,
 }
 
 pub(crate) struct AttributeParseError {
@@ -600,11 +601,11 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for AttributeParseError {
                 diag.code(E0538);
             }
             AttributeParseErrorReason::UnexpectedLiteral => {
-                diag.span_label(self.span, format!("didn't expect a literal here"));
+                diag.span_label(self.span, "didn't expect a literal here");
                 diag.code(E0565);
             }
             AttributeParseErrorReason::ExpectedNoArgs => {
-                diag.span_label(self.span, format!("didn't expect any arguments here"));
+                diag.span_label(self.span, "didn't expect any arguments here");
                 diag.code(E0565);
             }
             AttributeParseErrorReason::ExpectedNameValue(None) => {
@@ -684,6 +685,9 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for AttributeParseError {
                     }
                 }
             }
+            AttributeParseErrorReason::ExpectedIdentifier => {
+                diag.span_label(self.span, "expected a valid identifier here");
+            }
         }
 
         let suggestions = self.template.suggestions(false, &name);

compiler/rustc_borrowck/src/diagnostics/move_errors.rs

@@ -115,10 +115,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
     fn append_to_grouped_errors(
         &self,
         grouped_errors: &mut Vec<GroupedMoveError<'tcx>>,
-        error: MoveError<'tcx>,
+        MoveError { place: original_path, location, kind }: MoveError<'tcx>,
     ) {
-        let MoveError { place: original_path, location, kind } = error;
-
         // Note: that the only time we assign a place isn't a temporary
         // to a user variable is when initializing it.
         // If that ever stops being the case, then the ever initialized
@@ -251,62 +249,56 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
     }
 
     fn report(&mut self, error: GroupedMoveError<'tcx>) {
-        let (mut err, err_span) = {
-            let (span, use_spans, original_path, kind) = match error {
-                GroupedMoveError::MovesFromPlace { span, original_path, ref kind, .. }
-                | GroupedMoveError::MovesFromValue { span, original_path, ref kind, .. } => {
-                    (span, None, original_path, kind)
-                }
-                GroupedMoveError::OtherIllegalMove { use_spans, original_path, ref kind } => {
-                    (use_spans.args_or_use(), Some(use_spans), original_path, kind)
-                }
-            };
-            debug!(
-                "report: original_path={:?} span={:?}, kind={:?} \
-                   original_path.is_upvar_field_projection={:?}",
-                original_path,
-                span,
-                kind,
-                self.is_upvar_field_projection(original_path.as_ref())
-            );
-            if self.has_ambiguous_copy(original_path.ty(self.body, self.infcx.tcx).ty) {
-                // If the type may implement Copy, skip the error.
-                // It's an error with the Copy implementation (e.g. duplicate Copy) rather than borrow check
-                self.dcx().span_delayed_bug(
-                    span,
-                    "Type may implement copy, but there is no other error.",
-                );
-                return;
+        let (span, use_spans, original_path, kind) = match error {
+            GroupedMoveError::MovesFromPlace { span, original_path, ref kind, .. }
+            | GroupedMoveError::MovesFromValue { span, original_path, ref kind, .. } => {
+                (span, None, original_path, kind)
+            }
+            GroupedMoveError::OtherIllegalMove { use_spans, original_path, ref kind } => {
+                (use_spans.args_or_use(), Some(use_spans), original_path, kind)
+            }
+        };
+        debug!(
+            "report: original_path={:?} span={:?}, kind={:?} \
+             original_path.is_upvar_field_projection={:?}",
+            original_path,
+            span,
+            kind,
+            self.is_upvar_field_projection(original_path.as_ref())
+        );
+        if self.has_ambiguous_copy(original_path.ty(self.body, self.infcx.tcx).ty) {
+            // If the type may implement Copy, skip the error.
+            // It's an error with the Copy implementation (e.g. duplicate Copy) rather than borrow check
+            self.dcx()
+                .span_delayed_bug(span, "Type may implement copy, but there is no other error.");
+            return;
+        }
+        let mut err = match kind {
+            &IllegalMoveOriginKind::BorrowedContent { target_place } => self
+                .report_cannot_move_from_borrowed_content(
+                    original_path,
+                    target_place,
+                    span,
+                    use_spans,
+                ),
+            &IllegalMoveOriginKind::InteriorOfTypeWithDestructor { container_ty: ty } => {
+                self.cannot_move_out_of_interior_of_drop(span, ty)
+            }
+            &IllegalMoveOriginKind::InteriorOfSliceOrArray { ty, is_index } => {
+                self.cannot_move_out_of_interior_noncopy(span, ty, Some(is_index))
             }
-            (
-                match kind {
-                    &IllegalMoveOriginKind::BorrowedContent { target_place } => self
-                        .report_cannot_move_from_borrowed_content(
-                            original_path,
-                            target_place,
-                            span,
-                            use_spans,
-                        ),
-                    &IllegalMoveOriginKind::InteriorOfTypeWithDestructor { container_ty: ty } => {
-                        self.cannot_move_out_of_interior_of_drop(span, ty)
-                    }
-                    &IllegalMoveOriginKind::InteriorOfSliceOrArray { ty, is_index } => {
-                        self.cannot_move_out_of_interior_noncopy(span, ty, Some(is_index))
-                    }
-                },
-                span,
-            )
         };
 
-        self.add_move_hints(error, &mut err, err_span);
+        self.add_move_hints(error, &mut err, span);
         self.buffer_error(err);
     }
 
     fn has_ambiguous_copy(&mut self, ty: Ty<'tcx>) -> bool {
-        let Some(copy_trait_def) = self.infcx.tcx.lang_items().copy_trait() else { return false };
-        // This is only going to be ambiguous if there are incoherent impls, because otherwise
-        // ambiguity should never happen in MIR.
-        self.infcx.type_implements_trait(copy_trait_def, [ty], self.infcx.param_env).may_apply()
+        let Some(copy_def_id) = self.infcx.tcx.lang_items().copy_trait() else { return false };
+
+        // Avoid bogus move errors because of an incoherent `Copy` impl.
+        self.infcx.type_implements_trait(copy_def_id, [ty], self.infcx.param_env).may_apply()
+            && self.infcx.tcx.coherent_trait(copy_def_id).is_err()
     }
 
     fn report_cannot_move_from_static(&mut self, place: Place<'tcx>, span: Span) -> Diag<'infcx> {
@@ -482,7 +474,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 self.cannot_move_out_of_interior_noncopy(span, ty, None)
             }
             ty::Closure(def_id, closure_args)
-                if def_id.as_local() == Some(self.mir_def_id()) && upvar_field.is_some() =>
+                if def_id.as_local() == Some(self.mir_def_id())
+                    && let Some(upvar_field) = upvar_field =>
             {
                 let closure_kind_ty = closure_args.as_closure().kind_ty();
                 let closure_kind = match closure_kind_ty.to_opt_closure_kind() {
@@ -495,7 +488,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 let capture_description =
                     format!("captured variable in an `{closure_kind}` closure");
 
-                let upvar = &self.upvars[upvar_field.unwrap().index()];
+                let upvar = &self.upvars[upvar_field.index()];
                 let upvar_hir_id = upvar.get_root_variable();
                 let upvar_name = upvar.to_string(tcx);
                 let upvar_span = tcx.hir_span(upvar_hir_id);
@@ -605,7 +598,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
             }
             // No binding. Nothing to suggest.
             GroupedMoveError::OtherIllegalMove { ref original_path, use_spans, .. } => {
-                let use_span = use_spans.var_or_use();
+                let mut use_span = use_spans.var_or_use();
                 let place_ty = original_path.ty(self.body, self.infcx.tcx).ty;
                 let place_desc = match self.describe_place(original_path.as_ref()) {
                     Some(desc) => format!("`{desc}`"),
@@ -622,6 +615,36 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                     );
                 }
 
+                if let Some(upvar_field) = self
+                    .prefixes(original_path.as_ref(), PrefixSet::All)
+                    .find_map(|p| self.is_upvar_field_projection(p))
+                {
+                    // Look for the introduction of the original binding being moved.
+                    let upvar = &self.upvars[upvar_field.index()];
+                    let upvar_hir_id = upvar.get_root_variable();
+                    use_span = match self.infcx.tcx.parent_hir_node(upvar_hir_id) {
+                        hir::Node::Param(param) => {
+                            // Instead of pointing at the path where we access the value within a
+                            // closure, we point at the type of the outer `fn` argument.
+                            param.ty_span
+                        }
+                        hir::Node::LetStmt(stmt) => match (stmt.ty, stmt.init) {
+                            // We point at the type of the outer let-binding.
+                            (Some(ty), _) => ty.span,
+                            // We point at the initializer of the outer let-binding, but only if it
+                            // isn't something that spans multiple lines, like a closure, as the
+                            // ASCII art gets messy.
+                            (None, Some(init))
+                                if !self.infcx.tcx.sess.source_map().is_multiline(init.span) =>
+                            {
+                                init.span
+                            }
+                            _ => use_span,
+                        },
+                        _ => use_span,
+                    };
+                }
+
                 err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Label {
                     is_partial_move: false,
                     ty: place_ty,
@@ -629,12 +652,22 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                     span: use_span,
                 });
 
+                let mut pointed_at_span = false;
                 use_spans.args_subdiag(err, |args_span| {
+                    if args_span == span || args_span == use_span {
+                        pointed_at_span = true;
+                    }
                     crate::session_diagnostics::CaptureArgLabel::MoveOutPlace {
-                        place: place_desc,
+                        place: place_desc.clone(),
                         args_span,
                     }
                 });
+                if !pointed_at_span && use_span != span {
+                    err.subdiagnostic(crate::session_diagnostics::CaptureArgLabel::MoveOutPlace {
+                        place: place_desc,
+                        args_span: span,
+                    });
+                }
 
                 self.add_note_for_packed_struct_derive(err, original_path.local);
             }

compiler/rustc_codegen_cranelift/src/constant.rs

@@ -74,7 +74,7 @@ pub(crate) fn codegen_tls_ref<'tcx>(
 pub(crate) fn eval_mir_constant<'tcx>(
     fx: &FunctionCx<'_, '_, 'tcx>,
     constant: &ConstOperand<'tcx>,
-) -> (ConstValue<'tcx>, Ty<'tcx>) {
+) -> (ConstValue, Ty<'tcx>) {
     let cv = fx.monomorphize(constant.const_);
     // This cannot fail because we checked all required_consts in advance.
     let val = cv
@@ -93,7 +93,7 @@ pub(crate) fn codegen_constant_operand<'tcx>(
 
 pub(crate) fn codegen_const_value<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
-    const_val: ConstValue<'tcx>,
+    const_val: ConstValue,
     ty: Ty<'tcx>,
 ) -> CValue<'tcx> {
     let layout = fx.layout_of(ty);
@@ -210,8 +210,7 @@ pub(crate) fn codegen_const_value<'tcx>(
                 .offset_i64(fx, i64::try_from(offset.bytes()).unwrap()),
             layout,
         ),
-        ConstValue::Slice { data, meta } => {
-            let alloc_id = fx.tcx.reserve_and_set_memory_alloc(data);
+        ConstValue::Slice { alloc_id, meta } => {
             let ptr = pointer_for_allocation(fx, alloc_id).get_addr(fx);
             let len = fx.bcx.ins().iconst(fx.pointer_type, meta as i64);
             CValue::by_val_pair(ptr, len, layout)

compiler/rustc_codegen_gcc/build_system/src/test.rs

@@ -588,7 +588,7 @@ fn asm_tests(env: &Env, args: &TestArg) -> Result<(), String> {
             &"always",
             &"--stage",
             &"0",
-            &"tests/assembly/asm",
+            &"tests/assembly-llvm/asm",
             &"--compiletest-rustc-args",
             &rustc_args,
         ],

compiler/rustc_codegen_gcc/messages.ftl

@@ -3,12 +3,4 @@ codegen_gcc_unwinding_inline_asm =
 
 codegen_gcc_copy_bitcode = failed to copy bitcode to object file: {$err}
 
-codegen_gcc_dynamic_linking_with_lto =
-    cannot prefer dynamic linking when performing LTO
-    .note = only 'staticlib', 'bin', and 'cdylib' outputs are supported with LTO
-
-codegen_gcc_lto_disallowed = lto can only be run for executables, cdylibs and static library outputs
-
-codegen_gcc_lto_dylib = lto cannot be used for `dylib` crate type without `-Zdylib-lto`
-
 codegen_gcc_lto_bitcode_from_rlib = failed to get bitcode from object file for LTO ({$gcc_err})

compiler/rustc_codegen_gcc/src/back/lto.rs

@@ -25,35 +25,21 @@ use std::sync::Arc;
 use gccjit::{Context, OutputKind};
 use object::read::archive::ArchiveFile;
 use rustc_codegen_ssa::back::lto::{SerializedModule, ThinModule, ThinShared};
-use rustc_codegen_ssa::back::symbol_export;
 use rustc_codegen_ssa::back::write::{CodegenContext, FatLtoInput};
 use rustc_codegen_ssa::traits::*;
 use rustc_codegen_ssa::{ModuleCodegen, ModuleKind, looks_like_rust_object_file};
 use rustc_data_structures::memmap::Mmap;
 use rustc_errors::{DiagCtxtHandle, FatalError};
-use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::bug;
 use rustc_middle::dep_graph::WorkProduct;
-use rustc_middle::middle::exported_symbols::{SymbolExportInfo, SymbolExportLevel};
-use rustc_session::config::{CrateType, Lto};
+use rustc_session::config::Lto;
 use rustc_target::spec::RelocModel;
 use tempfile::{TempDir, tempdir};
 
 use crate::back::write::save_temp_bitcode;
-use crate::errors::{DynamicLinkingWithLTO, LtoBitcodeFromRlib, LtoDisallowed, LtoDylib};
+use crate::errors::LtoBitcodeFromRlib;
 use crate::{GccCodegenBackend, GccContext, SyncContext, to_gcc_opt_level};
 
-pub fn crate_type_allows_lto(crate_type: CrateType) -> bool {
-    match crate_type {
-        CrateType::Executable
-        | CrateType::Dylib
-        | CrateType::Staticlib
-        | CrateType::Cdylib
-        | CrateType::Sdylib => true,
-        CrateType::Rlib | CrateType::ProcMacro => false,
-    }
-}
-
 struct LtoData {
     // TODO(antoyo): use symbols_below_threshold.
     //symbols_below_threshold: Vec<String>,
@@ -63,18 +49,9 @@ struct LtoData {
 
 fn prepare_lto(
     cgcx: &CodegenContext<GccCodegenBackend>,
+    each_linked_rlib_for_lto: &[PathBuf],
     dcx: DiagCtxtHandle<'_>,
 ) -> Result<LtoData, FatalError> {
-    let export_threshold = match cgcx.lto {
-        // We're just doing LTO for our one crate
-        Lto::ThinLocal => SymbolExportLevel::Rust,
-
-        // We're doing LTO for the entire crate graph
-        Lto::Fat | Lto::Thin => symbol_export::crates_export_threshold(&cgcx.crate_types),
-
-        Lto::No => panic!("didn't request LTO but we're doing LTO"),
-    };
-
     let tmp_path = match tempdir() {
         Ok(tmp_path) => tmp_path,
         Err(error) => {
@@ -83,20 +60,6 @@ fn prepare_lto(
         }
     };
 
-    let symbol_filter = &|&(ref name, info): &(String, SymbolExportInfo)| {
-        if info.level.is_below_threshold(export_threshold) || info.used {
-            Some(name.clone())
-        } else {
-            None
-        }
-    };
-    let exported_symbols = cgcx.exported_symbols.as_ref().expect("needs exported symbols for LTO");
-    let mut symbols_below_threshold = {
-        let _timer = cgcx.prof.generic_activity("GCC_lto_generate_symbols_below_threshold");
-        exported_symbols[&LOCAL_CRATE].iter().filter_map(symbol_filter).collect::<Vec<String>>()
-    };
-    info!("{} symbols to preserve in this crate", symbols_below_threshold.len());
-
     // If we're performing LTO for the entire crate graph, then for each of our
     // upstream dependencies, find the corresponding rlib and load the bitcode
     // from the archive.
@@ -105,32 +68,7 @@ fn prepare_lto(
     // with either fat or thin LTO
     let mut upstream_modules = Vec::new();
     if cgcx.lto != Lto::ThinLocal {
-        // Make sure we actually can run LTO
-        for crate_type in cgcx.crate_types.iter() {
-            if !crate_type_allows_lto(*crate_type) {
-                dcx.emit_err(LtoDisallowed);
-                return Err(FatalError);
-            }
-            if *crate_type == CrateType::Dylib && !cgcx.opts.unstable_opts.dylib_lto {
-                dcx.emit_err(LtoDylib);
-                return Err(FatalError);
-            }
-        }
-
-        if cgcx.opts.cg.prefer_dynamic && !cgcx.opts.unstable_opts.dylib_lto {
-            dcx.emit_err(DynamicLinkingWithLTO);
-            return Err(FatalError);
-        }
-
-        for &(cnum, ref path) in cgcx.each_linked_rlib_for_lto.iter() {
-            let exported_symbols =
-                cgcx.exported_symbols.as_ref().expect("needs exported symbols for LTO");
-            {
-                let _timer = cgcx.prof.generic_activity("GCC_lto_generate_symbols_below_threshold");
-                symbols_below_threshold
-                    .extend(exported_symbols[&cnum].iter().filter_map(symbol_filter));
-            }
-
+        for path in each_linked_rlib_for_lto {
             let archive_data = unsafe {
                 Mmap::map(File::open(path).expect("couldn't open rlib")).expect("couldn't map rlib")
             };
@@ -174,19 +112,18 @@ fn save_as_file(obj: &[u8], path: &Path) -> Result<(), LtoBitcodeFromRlib> {
 /// for further optimization.
 pub(crate) fn run_fat(
     cgcx: &CodegenContext<GccCodegenBackend>,
+    each_linked_rlib_for_lto: &[PathBuf],
     modules: Vec<FatLtoInput<GccCodegenBackend>>,
-    cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>,
 ) -> Result<ModuleCodegen<GccContext>, FatalError> {
     let dcx = cgcx.create_dcx();
     let dcx = dcx.handle();
-    let lto_data = prepare_lto(cgcx, dcx)?;
+    let lto_data = prepare_lto(cgcx, each_linked_rlib_for_lto, dcx)?;
     /*let symbols_below_threshold =
     lto_data.symbols_below_threshold.iter().map(|c| c.as_ptr()).collect::<Vec<_>>();*/
     fat_lto(
         cgcx,
         dcx,
         modules,
-        cached_modules,
         lto_data.upstream_modules,
         lto_data.tmp_path,
         //&lto_data.symbols_below_threshold,
@@ -197,7 +134,6 @@ fn fat_lto(
     cgcx: &CodegenContext<GccCodegenBackend>,
     _dcx: DiagCtxtHandle<'_>,
     modules: Vec<FatLtoInput<GccCodegenBackend>>,
-    cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>,
     mut serialized_modules: Vec<(SerializedModule<ModuleBuffer>, CString)>,
     tmp_path: TempDir,
     //symbols_below_threshold: &[String],
@@ -211,21 +147,12 @@ fn fat_lto(
     //   modules that are serialized in-memory.
     // * `in_memory` contains modules which are already parsed and in-memory,
     //   such as from multi-CGU builds.
-    //
-    // All of `cached_modules` (cached from previous incremental builds) can
-    // immediately go onto the `serialized_modules` modules list and then we can
-    // split the `modules` array into these two lists.
     let mut in_memory = Vec::new();
-    serialized_modules.extend(cached_modules.into_iter().map(|(buffer, wp)| {
-        info!("pushing cached module {:?}", wp.cgu_name);
-        (buffer, CString::new(wp.cgu_name).unwrap())
-    }));
     for module in modules {
         match module {
             FatLtoInput::InMemory(m) => in_memory.push(m),
             FatLtoInput::Serialized { name, buffer } => {
                 info!("pushing serialized module {:?}", name);
-                let buffer = SerializedModule::Local(buffer);
                 serialized_modules.push((buffer, CString::new(name).unwrap()));
             }
         }
@@ -356,12 +283,13 @@ impl ModuleBufferMethods for ModuleBuffer {
 /// can simply be copied over from the incr. comp. cache.
 pub(crate) fn run_thin(
     cgcx: &CodegenContext<GccCodegenBackend>,
+    each_linked_rlib_for_lto: &[PathBuf],
     modules: Vec<(String, ThinBuffer)>,
     cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>,
 ) -> Result<(Vec<ThinModule<GccCodegenBackend>>, Vec<WorkProduct>), FatalError> {
     let dcx = cgcx.create_dcx();
     let dcx = dcx.handle();
-    let lto_data = prepare_lto(cgcx, dcx)?;
+    let lto_data = prepare_lto(cgcx, each_linked_rlib_for_lto, dcx)?;
     if cgcx.opts.cg.linker_plugin_lto.enabled() {
         unreachable!(
             "We should never reach this case if the LTO step \

compiler/rustc_codegen_gcc/src/errors.rs

@@ -14,19 +14,6 @@ pub(crate) struct CopyBitcode {
     pub err: std::io::Error,
 }
 
-#[derive(Diagnostic)]
-#[diag(codegen_gcc_dynamic_linking_with_lto)]
-#[note]
-pub(crate) struct DynamicLinkingWithLTO;
-
-#[derive(Diagnostic)]
-#[diag(codegen_gcc_lto_disallowed)]
-pub(crate) struct LtoDisallowed;
-
-#[derive(Diagnostic)]
-#[diag(codegen_gcc_lto_dylib)]
-pub(crate) struct LtoDylib;
-
 #[derive(Diagnostic)]
 #[diag(codegen_gcc_lto_bitcode_from_rlib)]
 pub(crate) struct LtoBitcodeFromRlib {

compiler/rustc_codegen_gcc/src/lib.rs

@@ -81,6 +81,7 @@ mod type_of;
 use std::any::Any;
 use std::fmt::Debug;
 use std::ops::Deref;
+use std::path::PathBuf;
 #[cfg(not(feature = "master"))]
 use std::sync::atomic::AtomicBool;
 #[cfg(not(feature = "master"))]
@@ -358,23 +359,28 @@ impl WriteBackendMethods for GccCodegenBackend {
 
     fn run_and_optimize_fat_lto(
         cgcx: &CodegenContext<Self>,
+        // FIXME(bjorn3): Limit LTO exports to these symbols
+        _exported_symbols_for_lto: &[String],
+        each_linked_rlib_for_lto: &[PathBuf],
         modules: Vec<FatLtoInput<Self>>,
-        cached_modules: Vec<(SerializedModule<Self::ModuleBuffer>, WorkProduct)>,
         diff_fncs: Vec<AutoDiffItem>,
     ) -> Result<ModuleCodegen<Self::Module>, FatalError> {
         if !diff_fncs.is_empty() {
             unimplemented!();
         }
 
-        back::lto::run_fat(cgcx, modules, cached_modules)
+        back::lto::run_fat(cgcx, each_linked_rlib_for_lto, modules)
     }
 
     fn run_thin_lto(
         cgcx: &CodegenContext<Self>,
+        // FIXME(bjorn3): Limit LTO exports to these symbols
+        _exported_symbols_for_lto: &[String],
+        each_linked_rlib_for_lto: &[PathBuf],
         modules: Vec<(String, Self::ThinBuffer)>,
         cached_modules: Vec<(SerializedModule<Self::ModuleBuffer>, WorkProduct)>,
     ) -> Result<(Vec<ThinModule<Self>>, Vec<WorkProduct>), FatalError> {
-        back::lto::run_thin(cgcx, modules, cached_modules)
+        back::lto::run_thin(cgcx, each_linked_rlib_for_lto, modules, cached_modules)
     }
 
     fn print_pass_timings(&self) {

compiler/rustc_codegen_llvm/messages.ftl

@@ -2,10 +2,6 @@ codegen_llvm_autodiff_without_enable = using the autodiff feature requires -Z au
 
 codegen_llvm_copy_bitcode = failed to copy bitcode to object file: {$err}
 
-codegen_llvm_dynamic_linking_with_lto =
-    cannot prefer dynamic linking when performing LTO
-    .note = only 'staticlib', 'bin', and 'cdylib' outputs are supported with LTO
-
 
 codegen_llvm_fixed_x18_invalid_arch = the `-Zfixed-x18` flag is not supported on the `{$arch}` architecture
 
@@ -18,12 +14,6 @@ codegen_llvm_load_bitcode_with_llvm_err = failed to load bitcode of module "{$na
 
 codegen_llvm_lto_bitcode_from_rlib = failed to get bitcode from object file for LTO ({$llvm_err})
 
-codegen_llvm_lto_disallowed = lto can only be run for executables, cdylibs and static library outputs
-
-codegen_llvm_lto_dylib = lto cannot be used for `dylib` crate type without `-Zdylib-lto`
-
-codegen_llvm_lto_proc_macro = lto cannot be used for `proc-macro` crate type without `-Zdylib-lto`
-
 codegen_llvm_mismatch_data_layout =
     data-layout for target `{$rustc_target}`, `{$rustc_layout}`, differs from LLVM target's `{$llvm_target}` default layout, `{$llvm_layout}`
 

compiler/rustc_codegen_llvm/src/back/lto.rs

@@ -1,33 +1,28 @@
 use std::collections::BTreeMap;
 use std::ffi::{CStr, CString};
 use std::fs::File;
-use std::path::Path;
+use std::path::{Path, PathBuf};
 use std::ptr::NonNull;
 use std::sync::Arc;
 use std::{io, iter, slice};
 
 use object::read::archive::ArchiveFile;
 use rustc_codegen_ssa::back::lto::{SerializedModule, ThinModule, ThinShared};
-use rustc_codegen_ssa::back::symbol_export;
 use rustc_codegen_ssa::back::write::{CodegenContext, FatLtoInput};
 use rustc_codegen_ssa::traits::*;
 use rustc_codegen_ssa::{ModuleCodegen, ModuleKind, looks_like_rust_object_file};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::memmap::Mmap;
 use rustc_errors::{DiagCtxtHandle, FatalError};
-use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::bug;
 use rustc_middle::dep_graph::WorkProduct;
-use rustc_middle::middle::exported_symbols::{SymbolExportInfo, SymbolExportLevel};
-use rustc_session::config::{self, CrateType, Lto};
+use rustc_session::config::{self, Lto};
 use tracing::{debug, info};
 
 use crate::back::write::{
     self, CodegenDiagnosticsStage, DiagnosticHandlers, bitcode_section_name, save_temp_bitcode,
 };
-use crate::errors::{
-    DynamicLinkingWithLTO, LlvmError, LtoBitcodeFromRlib, LtoDisallowed, LtoDylib, LtoProcMacro,
-};
+use crate::errors::{LlvmError, LtoBitcodeFromRlib};
 use crate::llvm::AttributePlace::Function;
 use crate::llvm::{self, build_string};
 use crate::{LlvmCodegenBackend, ModuleLlvm, SimpleCx, attributes};
@@ -36,45 +31,21 @@ use crate::{LlvmCodegenBackend, ModuleLlvm, SimpleCx, attributes};
 /// session to determine which CGUs we can reuse.
 const THIN_LTO_KEYS_INCR_COMP_FILE_NAME: &str = "thin-lto-past-keys.bin";
 
-fn crate_type_allows_lto(crate_type: CrateType) -> bool {
-    match crate_type {
-        CrateType::Executable
-        | CrateType::Dylib
-        | CrateType::Staticlib
-        | CrateType::Cdylib
-        | CrateType::ProcMacro
-        | CrateType::Sdylib => true,
-        CrateType::Rlib => false,
-    }
-}
-
 fn prepare_lto(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
+    exported_symbols_for_lto: &[String],
+    each_linked_rlib_for_lto: &[PathBuf],
     dcx: DiagCtxtHandle<'_>,
 ) -> Result<(Vec<CString>, Vec<(SerializedModule<ModuleBuffer>, CString)>), FatalError> {
-    let export_threshold = match cgcx.lto {
-        // We're just doing LTO for our one crate
-        Lto::ThinLocal => SymbolExportLevel::Rust,
+    let mut symbols_below_threshold = exported_symbols_for_lto
+        .iter()
+        .map(|symbol| CString::new(symbol.to_owned()).unwrap())
+        .collect::<Vec<CString>>();
 
-        // We're doing LTO for the entire crate graph
-        Lto::Fat | Lto::Thin => symbol_export::crates_export_threshold(&cgcx.crate_types),
-
-        Lto::No => panic!("didn't request LTO but we're doing LTO"),
-    };
-
-    let symbol_filter = &|&(ref name, info): &(String, SymbolExportInfo)| {
-        if info.level.is_below_threshold(export_threshold) || info.used {
-            Some(CString::new(name.as_str()).unwrap())
-        } else {
-            None
-        }
-    };
-    let exported_symbols = cgcx.exported_symbols.as_ref().expect("needs exported symbols for LTO");
-    let mut symbols_below_threshold = {
-        let _timer = cgcx.prof.generic_activity("LLVM_lto_generate_symbols_below_threshold");
-        exported_symbols[&LOCAL_CRATE].iter().filter_map(symbol_filter).collect::<Vec<CString>>()
-    };
-    info!("{} symbols to preserve in this crate", symbols_below_threshold.len());
+    // __llvm_profile_counter_bias is pulled in at link time by an undefined reference to
+    // __llvm_profile_runtime, therefore we won't know until link time if this symbol
+    // should have default visibility.
+    symbols_below_threshold.push(c"__llvm_profile_counter_bias".to_owned());
 
     // If we're performing LTO for the entire crate graph, then for each of our
     // upstream dependencies, find the corresponding rlib and load the bitcode
@@ -84,37 +55,7 @@ fn prepare_lto(
     // with either fat or thin LTO
     let mut upstream_modules = Vec::new();
     if cgcx.lto != Lto::ThinLocal {
-        // Make sure we actually can run LTO
-        for crate_type in cgcx.crate_types.iter() {
-            if !crate_type_allows_lto(*crate_type) {
-                dcx.emit_err(LtoDisallowed);
-                return Err(FatalError);
-            } else if *crate_type == CrateType::Dylib {
-                if !cgcx.opts.unstable_opts.dylib_lto {
-                    dcx.emit_err(LtoDylib);
-                    return Err(FatalError);
-                }
-            } else if *crate_type == CrateType::ProcMacro && !cgcx.opts.unstable_opts.dylib_lto {
-                dcx.emit_err(LtoProcMacro);
-                return Err(FatalError);
-            }
-        }
-
-        if cgcx.opts.cg.prefer_dynamic && !cgcx.opts.unstable_opts.dylib_lto {
-            dcx.emit_err(DynamicLinkingWithLTO);
-            return Err(FatalError);
-        }
-
-        for &(cnum, ref path) in cgcx.each_linked_rlib_for_lto.iter() {
-            let exported_symbols =
-                cgcx.exported_symbols.as_ref().expect("needs exported symbols for LTO");
-            {
-                let _timer =
-                    cgcx.prof.generic_activity("LLVM_lto_generate_symbols_below_threshold");
-                symbols_below_threshold
-                    .extend(exported_symbols[&cnum].iter().filter_map(symbol_filter));
-            }
-
+        for path in each_linked_rlib_for_lto {
             let archive_data = unsafe {
                 Mmap::map(std::fs::File::open(&path).expect("couldn't open rlib"))
                     .expect("couldn't map rlib")
@@ -147,10 +88,6 @@ fn prepare_lto(
         }
     }
 
-    // __llvm_profile_counter_bias is pulled in at link time by an undefined reference to
-    // __llvm_profile_runtime, therefore we won't know until link time if this symbol
-    // should have default visibility.
-    symbols_below_threshold.push(c"__llvm_profile_counter_bias".to_owned());
     Ok((symbols_below_threshold, upstream_modules))
 }
 
@@ -199,15 +136,17 @@ fn get_bitcode_slice_from_object_data<'a>(
 /// for further optimization.
 pub(crate) fn run_fat(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
+    exported_symbols_for_lto: &[String],
+    each_linked_rlib_for_lto: &[PathBuf],
     modules: Vec<FatLtoInput<LlvmCodegenBackend>>,
-    cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>,
 ) -> Result<ModuleCodegen<ModuleLlvm>, FatalError> {
     let dcx = cgcx.create_dcx();
     let dcx = dcx.handle();
-    let (symbols_below_threshold, upstream_modules) = prepare_lto(cgcx, dcx)?;
+    let (symbols_below_threshold, upstream_modules) =
+        prepare_lto(cgcx, exported_symbols_for_lto, each_linked_rlib_for_lto, dcx)?;
     let symbols_below_threshold =
         symbols_below_threshold.iter().map(|c| c.as_ptr()).collect::<Vec<_>>();
-    fat_lto(cgcx, dcx, modules, cached_modules, upstream_modules, &symbols_below_threshold)
+    fat_lto(cgcx, dcx, modules, upstream_modules, &symbols_below_threshold)
 }
 
 /// Performs thin LTO by performing necessary global analysis and returning two
@@ -215,12 +154,15 @@ pub(crate) fn run_fat(
 /// can simply be copied over from the incr. comp. cache.
 pub(crate) fn run_thin(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
+    exported_symbols_for_lto: &[String],
+    each_linked_rlib_for_lto: &[PathBuf],
     modules: Vec<(String, ThinBuffer)>,
     cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>,
 ) -> Result<(Vec<ThinModule<LlvmCodegenBackend>>, Vec<WorkProduct>), FatalError> {
     let dcx = cgcx.create_dcx();
     let dcx = dcx.handle();
-    let (symbols_below_threshold, upstream_modules) = prepare_lto(cgcx, dcx)?;
+    let (symbols_below_threshold, upstream_modules) =
+        prepare_lto(cgcx, exported_symbols_for_lto, each_linked_rlib_for_lto, dcx)?;
     let symbols_below_threshold =
         symbols_below_threshold.iter().map(|c| c.as_ptr()).collect::<Vec<_>>();
     if cgcx.opts.cg.linker_plugin_lto.enabled() {
@@ -245,7 +187,6 @@ fn fat_lto(
     cgcx: &CodegenContext<LlvmCodegenBackend>,
     dcx: DiagCtxtHandle<'_>,
     modules: Vec<FatLtoInput<LlvmCodegenBackend>>,
-    cached_modules: Vec<(SerializedModule<ModuleBuffer>, WorkProduct)>,
     mut serialized_modules: Vec<(SerializedModule<ModuleBuffer>, CString)>,
     symbols_below_threshold: &[*const libc::c_char],
 ) -> Result<ModuleCodegen<ModuleLlvm>, FatalError> {
@@ -258,21 +199,12 @@ fn fat_lto(
     //   modules that are serialized in-memory.
     // * `in_memory` contains modules which are already parsed and in-memory,
     //   such as from multi-CGU builds.
-    //
-    // All of `cached_modules` (cached from previous incremental builds) can
-    // immediately go onto the `serialized_modules` modules list and then we can
-    // split the `modules` array into these two lists.
     let mut in_memory = Vec::new();
-    serialized_modules.extend(cached_modules.into_iter().map(|(buffer, wp)| {
-        info!("pushing cached module {:?}", wp.cgu_name);
-        (buffer, CString::new(wp.cgu_name).unwrap())
-    }));
     for module in modules {
         match module {
             FatLtoInput::InMemory(m) => in_memory.push(m),
             FatLtoInput::Serialized { name, buffer } => {
                 info!("pushing serialized module {:?}", name);
-                let buffer = SerializedModule::Local(buffer);
                 serialized_modules.push((buffer, CString::new(name).unwrap()));
             }
         }

compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/spans.rs

@@ -39,7 +39,10 @@ impl Coords {
 /// or other expansions), and if it does happen then skipping a span or function is
 /// better than an ICE or `llvm-cov` failure that the user might have no way to avoid.
 pub(crate) fn make_coords(source_map: &SourceMap, file: &SourceFile, span: Span) -> Option<Coords> {
-    let span = ensure_non_empty_span(source_map, span)?;
+    if span.is_empty() {
+        debug_assert!(false, "can't make coords from empty span: {span:?}");
+        return None;
+    }
 
     let lo = span.lo();
     let hi = span.hi();
@@ -70,29 +73,6 @@ pub(crate) fn make_coords(source_map: &SourceMap, file: &SourceFile, span: Span)
     })
 }
 
-fn ensure_non_empty_span(source_map: &SourceMap, span: Span) -> Option<Span> {
-    if !span.is_empty() {
-        return Some(span);
-    }
-
-    // The span is empty, so try to enlarge it to cover an adjacent '{' or '}'.
-    source_map
-        .span_to_source(span, |src, start, end| try {
-            // Adjusting span endpoints by `BytePos(1)` is normally a bug,
-            // but in this case we have specifically checked that the character
-            // we're skipping over is one of two specific ASCII characters, so
-            // adjusting by exactly 1 byte is correct.
-            if src.as_bytes().get(end).copied() == Some(b'{') {
-                Some(span.with_hi(span.hi() + BytePos(1)))
-            } else if start > 0 && src.as_bytes()[start - 1] == b'}' {
-                Some(span.with_lo(span.lo() - BytePos(1)))
-            } else {
-                None
-            }
-        })
-        .ok()?
-}
-
 /// If `llvm-cov` sees a source region that is improperly ordered (end < start),
 /// it will immediately exit with a fatal error. To prevent that from happening,
 /// discard regions that are improperly ordered, or might be interpreted in a

compiler/rustc_codegen_llvm/src/errors.rs

@@ -20,11 +20,6 @@ pub(crate) struct SymbolAlreadyDefined<'a> {
 #[diag(codegen_llvm_sanitizer_memtag_requires_mte)]
 pub(crate) struct SanitizerMemtagRequiresMte;
 
-#[derive(Diagnostic)]
-#[diag(codegen_llvm_dynamic_linking_with_lto)]
-#[note]
-pub(crate) struct DynamicLinkingWithLTO;
-
 pub(crate) struct ParseTargetMachineConfig<'a>(pub LlvmError<'a>);
 
 impl<G: EmissionGuarantee> Diagnostic<'_, G> for ParseTargetMachineConfig<'_> {
@@ -41,18 +36,6 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for ParseTargetMachineConfig<'_> {
 #[diag(codegen_llvm_autodiff_without_enable)]
 pub(crate) struct AutoDiffWithoutEnable;
 
-#[derive(Diagnostic)]
-#[diag(codegen_llvm_lto_disallowed)]
-pub(crate) struct LtoDisallowed;
-
-#[derive(Diagnostic)]
-#[diag(codegen_llvm_lto_dylib)]
-pub(crate) struct LtoDylib;
-
-#[derive(Diagnostic)]
-#[diag(codegen_llvm_lto_proc_macro)]
-pub(crate) struct LtoProcMacro;
-
 #[derive(Diagnostic)]
 #[diag(codegen_llvm_lto_bitcode_from_rlib)]
 pub(crate) struct LtoBitcodeFromRlib {

compiler/rustc_codegen_llvm/src/lib.rs

@@ -22,6 +22,7 @@
 use std::any::Any;
 use std::ffi::CStr;
 use std::mem::ManuallyDrop;
+use std::path::PathBuf;
 
 use back::owned_target_machine::OwnedTargetMachine;
 use back::write::{create_informational_target_machine, create_target_machine};
@@ -176,11 +177,13 @@ impl WriteBackendMethods for LlvmCodegenBackend {
     }
     fn run_and_optimize_fat_lto(
         cgcx: &CodegenContext<Self>,
+        exported_symbols_for_lto: &[String],
+        each_linked_rlib_for_lto: &[PathBuf],
         modules: Vec<FatLtoInput<Self>>,
-        cached_modules: Vec<(SerializedModule<Self::ModuleBuffer>, WorkProduct)>,
         diff_fncs: Vec<AutoDiffItem>,
     ) -> Result<ModuleCodegen<Self::Module>, FatalError> {
-        let mut module = back::lto::run_fat(cgcx, modules, cached_modules)?;
+        let mut module =
+            back::lto::run_fat(cgcx, exported_symbols_for_lto, each_linked_rlib_for_lto, modules)?;
 
         if !diff_fncs.is_empty() {
             builder::autodiff::differentiate(&module, cgcx, diff_fncs)?;
@@ -194,10 +197,18 @@ impl WriteBackendMethods for LlvmCodegenBackend {
     }
     fn run_thin_lto(
         cgcx: &CodegenContext<Self>,
+        exported_symbols_for_lto: &[String],
+        each_linked_rlib_for_lto: &[PathBuf],
         modules: Vec<(String, Self::ThinBuffer)>,
         cached_modules: Vec<(SerializedModule<Self::ModuleBuffer>, WorkProduct)>,
     ) -> Result<(Vec<ThinModule<Self>>, Vec<WorkProduct>), FatalError> {
-        back::lto::run_thin(cgcx, modules, cached_modules)
+        back::lto::run_thin(
+            cgcx,
+            exported_symbols_for_lto,
+            each_linked_rlib_for_lto,
+            modules,
+            cached_modules,
+        )
     }
     fn optimize(
         cgcx: &CodegenContext<Self>,

compiler/rustc_codegen_ssa/messages.ftl

@@ -35,6 +35,10 @@ codegen_ssa_dlltool_fail_import_library =
     {$stdout}
     {$stderr}
 
+codegen_ssa_dynamic_linking_with_lto =
+    cannot prefer dynamic linking when performing LTO
+    .note = only 'staticlib', 'bin', and 'cdylib' outputs are supported with LTO
+
 codegen_ssa_error_calling_dlltool =
     Error calling dlltool '{$dlltool_path}': {$error}
 
@@ -191,6 +195,12 @@ codegen_ssa_linker_unsupported_modifier = `as-needed` modifier not supported for
 
 codegen_ssa_linking_failed = linking with `{$linker_path}` failed: {$exit_status}
 
+codegen_ssa_lto_disallowed = lto can only be run for executables, cdylibs and static library outputs
+
+codegen_ssa_lto_dylib = lto cannot be used for `dylib` crate type without `-Zdylib-lto`
+
+codegen_ssa_lto_proc_macro = lto cannot be used for `proc-macro` crate type without `-Zdylib-lto`
+
 codegen_ssa_malformed_cgu_name =
     found malformed codegen unit name `{$user_path}`. codegen units names must always start with the name of the crate (`{$crate_name}` in this case).
 

compiler/rustc_codegen_ssa/src/back/link/raw_dylib.rs

@@ -4,7 +4,7 @@ use std::path::{Path, PathBuf};
 
 use rustc_abi::Endian;
 use rustc_data_structures::base_n::{CASE_INSENSITIVE, ToBaseN};
-use rustc_data_structures::fx::FxIndexMap;
+use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_data_structures::stable_hasher::StableHasher;
 use rustc_hashes::Hash128;
 use rustc_session::Session;
@@ -214,7 +214,7 @@ pub(super) fn create_raw_dylib_elf_stub_shared_objects<'a>(
 /// It exports all the provided symbols, but is otherwise empty.
 fn create_elf_raw_dylib_stub(sess: &Session, soname: &str, symbols: &[DllImport]) -> Vec<u8> {
     use object::write::elf as write;
-    use object::{Architecture, elf};
+    use object::{AddressSize, Architecture, elf};
 
     let mut stub_buf = Vec::new();
 
@@ -226,47 +226,6 @@ fn create_elf_raw_dylib_stub(sess: &Session, soname: &str, symbols: &[DllImport]
     // It is important that the order of reservation matches the order of writing.
     // The object crate contains many debug asserts that fire if you get this wrong.
 
-    let endianness = match sess.target.options.endian {
-        Endian::Little => object::Endianness::Little,
-        Endian::Big => object::Endianness::Big,
-    };
-    let mut stub = write::Writer::new(endianness, true, &mut stub_buf);
-
-    // These initial reservations don't reserve any bytes in the binary yet,
-    // they just allocate in the internal data structures.
-
-    // First, we crate the dynamic symbol table. It starts with a null symbol
-    // and then all the symbols and their dynamic strings.
-    stub.reserve_null_dynamic_symbol_index();
-
-    let dynstrs = symbols
-        .iter()
-        .map(|sym| {
-            stub.reserve_dynamic_symbol_index();
-            (sym, stub.add_dynamic_string(sym.name.as_str().as_bytes()))
-        })
-        .collect::<Vec<_>>();
-
-    let soname = stub.add_dynamic_string(soname.as_bytes());
-
-    // Reserve the sections.
-    // We have the minimal sections for a dynamic SO and .text where we point our dummy symbols to.
-    stub.reserve_shstrtab_section_index();
-    let text_section_name = stub.add_section_name(".text".as_bytes());
-    let text_section = stub.reserve_section_index();
-    stub.reserve_dynstr_section_index();
-    stub.reserve_dynsym_section_index();
-    stub.reserve_dynamic_section_index();
-
-    // These reservations now determine the actual layout order of the object file.
-    stub.reserve_file_header();
-    stub.reserve_shstrtab();
-    stub.reserve_section_headers();
-    stub.reserve_dynstr();
-    stub.reserve_dynsym();
-    stub.reserve_dynamic(2); // DT_SONAME, DT_NULL
-
-    // First write the ELF header with the arch information.
     let Some((arch, sub_arch)) = sess.target.object_architecture(&sess.unstable_target_features)
     else {
         sess.dcx().fatal(format!(
@@ -274,6 +233,87 @@ fn create_elf_raw_dylib_stub(sess: &Session, soname: &str, symbols: &[DllImport]
             sess.target.arch
         ));
     };
+
+    let endianness = match sess.target.options.endian {
+        Endian::Little => object::Endianness::Little,
+        Endian::Big => object::Endianness::Big,
+    };
+
+    let is_64 = match arch.address_size() {
+        Some(AddressSize::U8 | AddressSize::U16 | AddressSize::U32) => false,
+        Some(AddressSize::U64) => true,
+        _ => sess.dcx().fatal(format!(
+            "raw-dylib is not supported for the architecture `{}`",
+            sess.target.arch
+        )),
+    };
+
+    let mut stub = write::Writer::new(endianness, is_64, &mut stub_buf);
+
+    let mut vers = Vec::new();
+    let mut vers_map = FxHashMap::default();
+    let mut syms = Vec::new();
+
+    for symbol in symbols {
+        let symbol_name = symbol.name.as_str();
+        if let Some((name, version_name)) = symbol_name.split_once('@') {
+            assert!(!version_name.contains('@'));
+            let dynstr = stub.add_dynamic_string(name.as_bytes());
+            let ver = if let Some(&ver_id) = vers_map.get(version_name) {
+                ver_id
+            } else {
+                let id = vers.len();
+                vers_map.insert(version_name, id);
+                let dynstr = stub.add_dynamic_string(version_name.as_bytes());
+                vers.push((version_name, dynstr));
+                id
+            };
+            syms.push((name, dynstr, Some(ver)));
+        } else {
+            let dynstr = stub.add_dynamic_string(symbol_name.as_bytes());
+            syms.push((symbol_name, dynstr, None));
+        }
+    }
+
+    let soname = stub.add_dynamic_string(soname.as_bytes());
+
+    // These initial reservations don't reserve any bytes in the binary yet,
+    // they just allocate in the internal data structures.
+
+    // First, we create the dynamic symbol table. It starts with a null symbol
+    // and then all the symbols and their dynamic strings.
+    stub.reserve_null_dynamic_symbol_index();
+
+    for _ in syms.iter() {
+        stub.reserve_dynamic_symbol_index();
+    }
+
+    // Reserve the sections.
+    // We have the minimal sections for a dynamic SO and .text where we point our dummy symbols to.
+    stub.reserve_shstrtab_section_index();
+    let text_section_name = stub.add_section_name(".text".as_bytes());
+    let text_section = stub.reserve_section_index();
+    stub.reserve_dynsym_section_index();
+    stub.reserve_dynstr_section_index();
+    if !vers.is_empty() {
+        stub.reserve_gnu_versym_section_index();
+        stub.reserve_gnu_verdef_section_index();
+    }
+    stub.reserve_dynamic_section_index();
+
+    // These reservations now determine the actual layout order of the object file.
+    stub.reserve_file_header();
+    stub.reserve_shstrtab();
+    stub.reserve_section_headers();
+    stub.reserve_dynsym();
+    stub.reserve_dynstr();
+    if !vers.is_empty() {
+        stub.reserve_gnu_versym();
+        stub.reserve_gnu_verdef(1 + vers.len(), 1 + vers.len());
+    }
+    stub.reserve_dynamic(2); // DT_SONAME, DT_NULL
+
+    // First write the ELF header with the arch information.
     let e_machine = match (arch, sub_arch) {
         (Architecture::Aarch64, None) => elf::EM_AARCH64,
         (Architecture::Aarch64_Ilp32, None) => elf::EM_AARCH64,
@@ -342,18 +382,19 @@ fn create_elf_raw_dylib_stub(sess: &Session, soname: &str, symbols: &[DllImport]
         sh_addralign: 1,
         sh_entsize: 0,
     });
-    stub.write_dynstr_section_header(0);
     stub.write_dynsym_section_header(0, 1);
+    stub.write_dynstr_section_header(0);
+    if !vers.is_empty() {
+        stub.write_gnu_versym_section_header(0);
+        stub.write_gnu_verdef_section_header(0);
+    }
     stub.write_dynamic_section_header(0);
 
-    // .dynstr
-    stub.write_dynstr();
-
     // .dynsym
     stub.write_null_dynamic_symbol();
-    for (_, name) in dynstrs {
+    for (_name, dynstr, _ver) in syms.iter().copied() {
         stub.write_dynamic_symbol(&write::Sym {
-            name: Some(name),
+            name: Some(dynstr),
             st_info: (elf::STB_GLOBAL << 4) | elf::STT_NOTYPE,
             st_other: elf::STV_DEFAULT,
             section: Some(text_section),
@@ -363,10 +404,47 @@ fn create_elf_raw_dylib_stub(sess: &Session, soname: &str, symbols: &[DllImport]
         });
     }
 
+    // .dynstr
+    stub.write_dynstr();
+
+    // ld.bfd is unhappy if these sections exist without any symbols, so we only generate them when necessary.
+    if !vers.is_empty() {
+        // .gnu_version
+        stub.write_null_gnu_versym();
+        for (_name, _dynstr, ver) in syms.iter().copied() {
+            stub.write_gnu_versym(if let Some(ver) = ver {
+                assert!((2 + ver as u16) < elf::VERSYM_HIDDEN);
+                elf::VERSYM_HIDDEN | (2 + ver as u16)
+            } else {
+                1
+            });
+        }
+
+        // .gnu_version_d
+        stub.write_align_gnu_verdef();
+        stub.write_gnu_verdef(&write::Verdef {
+            version: elf::VER_DEF_CURRENT,
+            flags: elf::VER_FLG_BASE,
+            index: 1,
+            aux_count: 1,
+            name: soname,
+        });
+        for (ver, (_name, dynstr)) in vers.into_iter().enumerate() {
+            stub.write_gnu_verdef(&write::Verdef {
+                version: elf::VER_DEF_CURRENT,
+                flags: 0,
+                index: 2 + ver as u16,
+                aux_count: 1,
+                name: dynstr,
+            });
+        }
+    }
+
     // .dynamic
     // the DT_SONAME will be used by the linker to populate DT_NEEDED
     // which the loader uses to find the library.
     // DT_NULL terminates the .dynamic table.
+    stub.write_align_dynamic();
     stub.write_dynamic_string(elf::DT_SONAME, soname);
     stub.write_dynamic(elf::DT_NULL, 0);
 

compiler/rustc_codegen_ssa/src/back/lto.rs

@@ -2,7 +2,15 @@ use std::ffi::CString;
 use std::sync::Arc;
 
 use rustc_data_structures::memmap::Mmap;
+use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
+use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo, SymbolExportLevel};
+use rustc_middle::ty::TyCtxt;
+use rustc_session::config::{CrateType, Lto};
+use tracing::info;
 
+use crate::back::symbol_export::{self, symbol_name_for_instance_in_crate};
+use crate::back::write::CodegenContext;
+use crate::errors::{DynamicLinkingWithLTO, LtoDisallowed, LtoDylib, LtoProcMacro};
 use crate::traits::*;
 
 pub struct ThinModule<B: WriteBackendMethods> {
@@ -52,3 +60,86 @@ impl<M: ModuleBufferMethods> SerializedModule<M> {
         }
     }
 }
+
+fn crate_type_allows_lto(crate_type: CrateType) -> bool {
+    match crate_type {
+        CrateType::Executable
+        | CrateType::Dylib
+        | CrateType::Staticlib
+        | CrateType::Cdylib
+        | CrateType::ProcMacro
+        | CrateType::Sdylib => true,
+        CrateType::Rlib => false,
+    }
+}
+
+pub(super) fn exported_symbols_for_lto(
+    tcx: TyCtxt<'_>,
+    each_linked_rlib_for_lto: &[CrateNum],
+) -> Vec<String> {
+    let export_threshold = match tcx.sess.lto() {
+        // We're just doing LTO for our one crate
+        Lto::ThinLocal => SymbolExportLevel::Rust,
+
+        // We're doing LTO for the entire crate graph
+        Lto::Fat | Lto::Thin => symbol_export::crates_export_threshold(&tcx.crate_types()),
+
+        Lto::No => return vec![],
+    };
+
+    let copy_symbols = |cnum| {
+        tcx.exported_non_generic_symbols(cnum)
+            .iter()
+            .chain(tcx.exported_generic_symbols(cnum))
+            .filter_map(|&(s, info): &(ExportedSymbol<'_>, SymbolExportInfo)| {
+                if info.level.is_below_threshold(export_threshold) || info.used {
+                    Some(symbol_name_for_instance_in_crate(tcx, s, cnum))
+                } else {
+                    None
+                }
+            })
+            .collect::<Vec<_>>()
+    };
+    let mut symbols_below_threshold = {
+        let _timer = tcx.prof.generic_activity("lto_generate_symbols_below_threshold");
+        copy_symbols(LOCAL_CRATE)
+    };
+    info!("{} symbols to preserve in this crate", symbols_below_threshold.len());
+
+    // If we're performing LTO for the entire crate graph, then for each of our
+    // upstream dependencies, include their exported symbols.
+    if tcx.sess.lto() != Lto::ThinLocal {
+        for &cnum in each_linked_rlib_for_lto {
+            let _timer = tcx.prof.generic_activity("lto_generate_symbols_below_threshold");
+            symbols_below_threshold.extend(copy_symbols(cnum));
+        }
+    }
+
+    symbols_below_threshold
+}
+
+pub(super) fn check_lto_allowed<B: WriteBackendMethods>(cgcx: &CodegenContext<B>) {
+    if cgcx.lto == Lto::ThinLocal {
+        // Crate local LTO is always allowed
+        return;
+    }
+
+    let dcx = cgcx.create_dcx();
+
+    // Make sure we actually can run LTO
+    for crate_type in cgcx.crate_types.iter() {
+        if !crate_type_allows_lto(*crate_type) {
+            dcx.handle().emit_fatal(LtoDisallowed);
+        } else if *crate_type == CrateType::Dylib {
+            if !cgcx.opts.unstable_opts.dylib_lto {
+                dcx.handle().emit_fatal(LtoDylib);
+            }
+        } else if *crate_type == CrateType::ProcMacro && !cgcx.opts.unstable_opts.dylib_lto {
+            dcx.handle().emit_fatal(LtoProcMacro);
+        }
+    }
+
+    if cgcx.opts.cg.prefer_dynamic && !cgcx.opts.unstable_opts.dylib_lto {
+        dcx.handle().emit_fatal(DynamicLinkingWithLTO);
+    }
+}

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -9,7 +9,7 @@ use std::{fs, io, mem, str, thread};
 use rustc_abi::Size;
 use rustc_ast::attr;
 use rustc_ast::expand::autodiff_attrs::AutoDiffItem;
-use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::jobserver::{self, Acquired};
 use rustc_data_structures::memmap::Mmap;
 use rustc_data_structures::profiling::{SelfProfilerRef, VerboseTimingGuard};
@@ -20,14 +20,12 @@ use rustc_errors::{
     Suggestions,
 };
 use rustc_fs_util::link_or_copy;
-use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
 use rustc_incremental::{
     copy_cgu_workproduct_to_incr_comp_cache_dir, in_incr_comp_dir, in_incr_comp_dir_sess,
 };
 use rustc_metadata::fs::copy_to_stdout;
 use rustc_middle::bug;
 use rustc_middle::dep_graph::{WorkProduct, WorkProductId};
-use rustc_middle::middle::exported_symbols::SymbolExportInfo;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
 use rustc_session::config::{
@@ -40,7 +38,7 @@ use tracing::debug;
 
 use super::link::{self, ensure_removed};
 use super::lto::{self, SerializedModule};
-use super::symbol_export::symbol_name_for_instance_in_crate;
+use crate::back::lto::check_lto_allowed;
 use crate::errors::{AutodiffWithoutLto, ErrorCreatingRemarkDir};
 use crate::traits::*;
 use crate::{
@@ -332,8 +330,6 @@ pub type TargetMachineFactoryFn<B> = Arc<
         + Sync,
 >;
 
-type ExportedSymbols = FxHashMap<CrateNum, Arc<Vec<(String, SymbolExportInfo)>>>;
-
 /// Additional resources used by optimize_and_codegen (not module specific)
 #[derive(Clone)]
 pub struct CodegenContext<B: WriteBackendMethods> {
@@ -343,10 +339,8 @@ pub struct CodegenContext<B: WriteBackendMethods> {
     pub save_temps: bool,
     pub fewer_names: bool,
     pub time_trace: bool,
-    pub exported_symbols: Option<Arc<ExportedSymbols>>,
     pub opts: Arc<config::Options>,
     pub crate_types: Vec<CrateType>,
-    pub each_linked_rlib_for_lto: Vec<(CrateNum, PathBuf)>,
     pub output_filenames: Arc<OutputFilenames>,
     pub invocation_temp: Option<String>,
     pub regular_module_config: Arc<ModuleConfig>,
@@ -401,13 +395,21 @@ impl<B: WriteBackendMethods> CodegenContext<B> {
 
 fn generate_thin_lto_work<B: ExtraBackendMethods>(
     cgcx: &CodegenContext<B>,
+    exported_symbols_for_lto: &[String],
+    each_linked_rlib_for_lto: &[PathBuf],
     needs_thin_lto: Vec<(String, B::ThinBuffer)>,
     import_only_modules: Vec<(SerializedModule<B::ModuleBuffer>, WorkProduct)>,
 ) -> Vec<(WorkItem<B>, u64)> {
     let _prof_timer = cgcx.prof.generic_activity("codegen_thin_generate_lto_work");
 
-    let (lto_modules, copy_jobs) =
-        B::run_thin_lto(cgcx, needs_thin_lto, import_only_modules).unwrap_or_else(|e| e.raise());
+    let (lto_modules, copy_jobs) = B::run_thin_lto(
+        cgcx,
+        exported_symbols_for_lto,
+        each_linked_rlib_for_lto,
+        needs_thin_lto,
+        import_only_modules,
+    )
+    .unwrap_or_else(|e| e.raise());
     lto_modules
         .into_iter()
         .map(|module| {
@@ -723,6 +725,8 @@ pub(crate) enum WorkItem<B: WriteBackendMethods> {
     CopyPostLtoArtifacts(CachedModuleCodegen),
     /// Performs fat LTO on the given module.
     FatLto {
+        exported_symbols_for_lto: Arc<Vec<String>>,
+        each_linked_rlib_for_lto: Vec<PathBuf>,
         needs_fat_lto: Vec<FatLtoInput<B>>,
         import_only_modules: Vec<(SerializedModule<B::ModuleBuffer>, WorkProduct)>,
         autodiff: Vec<AutoDiffItem>,
@@ -810,7 +814,7 @@ pub(crate) enum WorkItemResult<B: WriteBackendMethods> {
 }
 
 pub enum FatLtoInput<B: WriteBackendMethods> {
-    Serialized { name: String, buffer: B::ModuleBuffer },
+    Serialized { name: String, buffer: SerializedModule<B::ModuleBuffer> },
     InMemory(ModuleCodegen<B::Module>),
 }
 
@@ -899,7 +903,10 @@ fn execute_optimize_work_item<B: ExtraBackendMethods>(
                 fs::write(&path, buffer.data()).unwrap_or_else(|e| {
                     panic!("Error writing pre-lto-bitcode file `{}`: {}", path.display(), e);
                 });
-                Ok(WorkItemResult::NeedsFatLto(FatLtoInput::Serialized { name, buffer }))
+                Ok(WorkItemResult::NeedsFatLto(FatLtoInput::Serialized {
+                    name,
+                    buffer: SerializedModule::Local(buffer),
+                }))
             }
             None => Ok(WorkItemResult::NeedsFatLto(FatLtoInput::InMemory(module))),
         },
@@ -992,12 +999,24 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
 
 fn execute_fat_lto_work_item<B: ExtraBackendMethods>(
     cgcx: &CodegenContext<B>,
-    needs_fat_lto: Vec<FatLtoInput<B>>,
+    exported_symbols_for_lto: &[String],
+    each_linked_rlib_for_lto: &[PathBuf],
+    mut needs_fat_lto: Vec<FatLtoInput<B>>,
     import_only_modules: Vec<(SerializedModule<B::ModuleBuffer>, WorkProduct)>,
     autodiff: Vec<AutoDiffItem>,
     module_config: &ModuleConfig,
 ) -> Result<WorkItemResult<B>, FatalError> {
-    let module = B::run_and_optimize_fat_lto(cgcx, needs_fat_lto, import_only_modules, autodiff)?;
+    for (module, wp) in import_only_modules {
+        needs_fat_lto.push(FatLtoInput::Serialized { name: wp.cgu_name, buffer: module })
+    }
+
+    let module = B::run_and_optimize_fat_lto(
+        cgcx,
+        exported_symbols_for_lto,
+        each_linked_rlib_for_lto,
+        needs_fat_lto,
+        autodiff,
+    )?;
     let module = B::codegen(cgcx, module, module_config)?;
     Ok(WorkItemResult::Finished(module))
 }
@@ -1032,7 +1051,7 @@ pub(crate) enum Message<B: WriteBackendMethods> {
 
     /// The backend has finished processing a work item for a codegen unit.
     /// Sent from a backend worker thread.
-    WorkItem { result: Result<WorkItemResult<B>, Option<WorkerFatalError>>, worker_id: usize },
+    WorkItem { result: Result<WorkItemResult<B>, Option<WorkerFatalError>> },
 
     /// The frontend has finished generating something (backend IR or a
     /// post-LTO artifact) for a codegen unit, and it should be passed to the
@@ -1113,42 +1132,18 @@ fn start_executing_work<B: ExtraBackendMethods>(
     let autodiff_items = autodiff_items.to_vec();
 
     let mut each_linked_rlib_for_lto = Vec::new();
+    let mut each_linked_rlib_file_for_lto = Vec::new();
     drop(link::each_linked_rlib(crate_info, None, &mut |cnum, path| {
         if link::ignored_for_lto(sess, crate_info, cnum) {
             return;
         }
-        each_linked_rlib_for_lto.push((cnum, path.to_path_buf()));
+        each_linked_rlib_for_lto.push(cnum);
+        each_linked_rlib_file_for_lto.push(path.to_path_buf());
     }));
 
     // Compute the set of symbols we need to retain when doing LTO (if we need to)
-    let exported_symbols = {
-        let mut exported_symbols = FxHashMap::default();
-
-        let copy_symbols = |cnum| {
-            let symbols = tcx
-                .exported_non_generic_symbols(cnum)
-                .iter()
-                .chain(tcx.exported_generic_symbols(cnum))
-                .map(|&(s, lvl)| (symbol_name_for_instance_in_crate(tcx, s, cnum), lvl))
-                .collect();
-            Arc::new(symbols)
-        };
-
-        match sess.lto() {
-            Lto::No => None,
-            Lto::ThinLocal => {
-                exported_symbols.insert(LOCAL_CRATE, copy_symbols(LOCAL_CRATE));
-                Some(Arc::new(exported_symbols))
-            }
-            Lto::Fat | Lto::Thin => {
-                exported_symbols.insert(LOCAL_CRATE, copy_symbols(LOCAL_CRATE));
-                for &(cnum, ref _path) in &each_linked_rlib_for_lto {
-                    exported_symbols.insert(cnum, copy_symbols(cnum));
-                }
-                Some(Arc::new(exported_symbols))
-            }
-        }
-    };
+    let exported_symbols_for_lto =
+        Arc::new(lto::exported_symbols_for_lto(tcx, &each_linked_rlib_for_lto));
 
     // First up, convert our jobserver into a helper thread so we can use normal
     // mpsc channels to manage our messages and such.
@@ -1183,14 +1178,12 @@ fn start_executing_work<B: ExtraBackendMethods>(
 
     let cgcx = CodegenContext::<B> {
         crate_types: tcx.crate_types().to_vec(),
-        each_linked_rlib_for_lto,
         lto: sess.lto(),
         fewer_names: sess.fewer_names(),
         save_temps: sess.opts.cg.save_temps,
         time_trace: sess.opts.unstable_opts.llvm_time_trace,
         opts: Arc::new(sess.opts.clone()),
         prof: sess.prof.clone(),
-        exported_symbols,
         remark: sess.opts.cg.remark.clone(),
         remark_dir,
         incr_comp_session_dir: sess.incr_comp_session_dir_opt().map(|r| r.clone()),
@@ -1350,18 +1343,6 @@ fn start_executing_work<B: ExtraBackendMethods>(
     // necessary. There's already optimizations in place to avoid sending work
     // back to the coordinator if LTO isn't requested.
     return B::spawn_named_thread(cgcx.time_trace, "coordinator".to_string(), move || {
-        let mut worker_id_counter = 0;
-        let mut free_worker_ids = Vec::new();
-        let mut get_worker_id = |free_worker_ids: &mut Vec<usize>| {
-            if let Some(id) = free_worker_ids.pop() {
-                id
-            } else {
-                let id = worker_id_counter;
-                worker_id_counter += 1;
-                id
-            }
-        };
-
         // This is where we collect codegen units that have gone all the way
         // through codegen and LLVM.
         let mut compiled_modules = vec![];
@@ -1442,12 +1423,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
                         let (item, _) =
                             work_items.pop().expect("queue empty - queue_full_enough() broken?");
                         main_thread_state = MainThreadState::Lending;
-                        spawn_work(
-                            &cgcx,
-                            &mut llvm_start_time,
-                            get_worker_id(&mut free_worker_ids),
-                            item,
-                        );
+                        spawn_work(&cgcx, &mut llvm_start_time, item);
                     }
                 }
             } else if codegen_state == Completed {
@@ -1474,12 +1450,18 @@ fn start_executing_work<B: ExtraBackendMethods>(
                     let needs_fat_lto = mem::take(&mut needs_fat_lto);
                     let needs_thin_lto = mem::take(&mut needs_thin_lto);
                     let import_only_modules = mem::take(&mut lto_import_only_modules);
+                    let each_linked_rlib_file_for_lto =
+                        mem::take(&mut each_linked_rlib_file_for_lto);
+
+                    check_lto_allowed(&cgcx);
 
                     if !needs_fat_lto.is_empty() {
                         assert!(needs_thin_lto.is_empty());
 
                         work_items.push((
                             WorkItem::FatLto {
+                                exported_symbols_for_lto: Arc::clone(&exported_symbols_for_lto),
+                                each_linked_rlib_for_lto: each_linked_rlib_file_for_lto,
                                 needs_fat_lto,
                                 import_only_modules,
                                 autodiff: autodiff_items.clone(),
@@ -1495,9 +1477,13 @@ fn start_executing_work<B: ExtraBackendMethods>(
                             dcx.handle().emit_fatal(AutodiffWithoutLto {});
                         }
 
-                        for (work, cost) in
-                            generate_thin_lto_work(&cgcx, needs_thin_lto, import_only_modules)
-                        {
+                        for (work, cost) in generate_thin_lto_work(
+                            &cgcx,
+                            &exported_symbols_for_lto,
+                            &each_linked_rlib_file_for_lto,
+                            needs_thin_lto,
+                            import_only_modules,
+                        ) {
                             let insertion_index = work_items
                                 .binary_search_by_key(&cost, |&(_, cost)| cost)
                                 .unwrap_or_else(|e| e);
@@ -1516,12 +1502,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
                     MainThreadState::Idle => {
                         if let Some((item, _)) = work_items.pop() {
                             main_thread_state = MainThreadState::Lending;
-                            spawn_work(
-                                &cgcx,
-                                &mut llvm_start_time,
-                                get_worker_id(&mut free_worker_ids),
-                                item,
-                            );
+                            spawn_work(&cgcx, &mut llvm_start_time, item);
                         } else {
                             // There is no unstarted work, so let the main thread
                             // take over for a running worker. Otherwise the
@@ -1557,12 +1538,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
                 while running_with_own_token < tokens.len()
                     && let Some((item, _)) = work_items.pop()
                 {
-                    spawn_work(
-                        &cgcx,
-                        &mut llvm_start_time,
-                        get_worker_id(&mut free_worker_ids),
-                        item,
-                    );
+                    spawn_work(&cgcx, &mut llvm_start_time, item);
                     running_with_own_token += 1;
                 }
             }
@@ -1570,21 +1546,6 @@ fn start_executing_work<B: ExtraBackendMethods>(
             // Relinquish accidentally acquired extra tokens.
             tokens.truncate(running_with_own_token);
 
-            // If a thread exits successfully then we drop a token associated
-            // with that worker and update our `running_with_own_token` count.
-            // We may later re-acquire a token to continue running more work.
-            // We may also not actually drop a token here if the worker was
-            // running with an "ephemeral token".
-            let mut free_worker = |worker_id| {
-                if main_thread_state == MainThreadState::Lending {
-                    main_thread_state = MainThreadState::Idle;
-                } else {
-                    running_with_own_token -= 1;
-                }
-
-                free_worker_ids.push(worker_id);
-            };
-
             let msg = coordinator_receive.recv().unwrap();
             match *msg.downcast::<Message<B>>().ok().unwrap() {
                 // Save the token locally and the next turn of the loop will use
@@ -1653,8 +1614,17 @@ fn start_executing_work<B: ExtraBackendMethods>(
                     codegen_state = Aborted;
                 }
 
-                Message::WorkItem { result, worker_id } => {
-                    free_worker(worker_id);
+                Message::WorkItem { result } => {
+                    // If a thread exits successfully then we drop a token associated
+                    // with that worker and update our `running_with_own_token` count.
+                    // We may later re-acquire a token to continue running more work.
+                    // We may also not actually drop a token here if the worker was
+                    // running with an "ephemeral token".
+                    if main_thread_state == MainThreadState::Lending {
+                        main_thread_state = MainThreadState::Idle;
+                    } else {
+                        running_with_own_token -= 1;
+                    }
 
                     match result {
                         Ok(WorkItemResult::Finished(compiled_module)) => {
@@ -1800,7 +1770,6 @@ pub(crate) struct WorkerFatalError;
 fn spawn_work<'a, B: ExtraBackendMethods>(
     cgcx: &'a CodegenContext<B>,
     llvm_start_time: &mut Option<VerboseTimingGuard<'a>>,
-    worker_id: usize,
     work: WorkItem<B>,
 ) {
     if cgcx.config(work.module_kind()).time_module && llvm_start_time.is_none() {
@@ -1815,24 +1784,21 @@ fn spawn_work<'a, B: ExtraBackendMethods>(
         struct Bomb<B: ExtraBackendMethods> {
             coordinator_send: Sender<Box<dyn Any + Send>>,
             result: Option<Result<WorkItemResult<B>, FatalError>>,
-            worker_id: usize,
         }
         impl<B: ExtraBackendMethods> Drop for Bomb<B> {
             fn drop(&mut self) {
-                let worker_id = self.worker_id;
                 let msg = match self.result.take() {
-                    Some(Ok(result)) => Message::WorkItem::<B> { result: Ok(result), worker_id },
+                    Some(Ok(result)) => Message::WorkItem::<B> { result: Ok(result) },
                     Some(Err(FatalError)) => {
-                        Message::WorkItem::<B> { result: Err(Some(WorkerFatalError)), worker_id }
+                        Message::WorkItem::<B> { result: Err(Some(WorkerFatalError)) }
                     }
-                    None => Message::WorkItem::<B> { result: Err(None), worker_id },
+                    None => Message::WorkItem::<B> { result: Err(None) },
                 };
                 drop(self.coordinator_send.send(Box::new(msg)));
             }
         }
 
-        let mut bomb =
-            Bomb::<B> { coordinator_send: cgcx.coordinator_send.clone(), result: None, worker_id };
+        let mut bomb = Bomb::<B> { coordinator_send: cgcx.coordinator_send.clone(), result: None };
 
         // Execute the work itself, and if it finishes successfully then flag
         // ourselves as a success as well.
@@ -1856,12 +1822,20 @@ fn spawn_work<'a, B: ExtraBackendMethods>(
                     );
                     Ok(execute_copy_from_cache_work_item(&cgcx, m, module_config))
                 }
-                WorkItem::FatLto { needs_fat_lto, import_only_modules, autodiff } => {
+                WorkItem::FatLto {
+                    exported_symbols_for_lto,
+                    each_linked_rlib_for_lto,
+                    needs_fat_lto,
+                    import_only_modules,
+                    autodiff,
+                } => {
                     let _timer = cgcx
                         .prof
                         .generic_activity_with_arg("codegen_module_perform_lto", "everything");
                     execute_fat_lto_work_item(
                         &cgcx,
+                        &exported_symbols_for_lto,
+                        &each_linked_rlib_for_lto,
                         needs_fat_lto,
                         import_only_modules,
                         autodiff,

compiler/rustc_codegen_ssa/src/common.rs

@@ -148,7 +148,7 @@ pub(crate) fn shift_mask_val<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 pub fn asm_const_to_str<'tcx>(
     tcx: TyCtxt<'tcx>,
     sp: Span,
-    const_value: mir::ConstValue<'tcx>,
+    const_value: mir::ConstValue,
     ty_and_layout: TyAndLayout<'tcx>,
 ) -> String {
     let mir::ConstValue::Scalar(scalar) = const_value else {

compiler/rustc_codegen_ssa/src/errors.rs

@@ -1294,3 +1294,20 @@ pub(crate) struct FeatureNotValid<'a> {
     #[help]
     pub plus_hint: bool,
 }
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_lto_disallowed)]
+pub(crate) struct LtoDisallowed;
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_lto_dylib)]
+pub(crate) struct LtoDylib;
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_lto_proc_macro)]
+pub(crate) struct LtoProcMacro;
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_dynamic_linking_with_lto)]
+#[note]
+pub(crate) struct DynamicLinkingWithLTO;

compiler/rustc_codegen_ssa/src/mir/constant.rs

@@ -20,7 +20,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         OperandRef::from_const(bx, val, ty)
     }
 
-    pub fn eval_mir_constant(&self, constant: &mir::ConstOperand<'tcx>) -> mir::ConstValue<'tcx> {
+    pub fn eval_mir_constant(&self, constant: &mir::ConstOperand<'tcx>) -> mir::ConstValue {
         // `MirUsedCollector` visited all required_consts before codegen began, so if we got here
         // there can be no more constants that fail to evaluate.
         self.monomorphize(constant.const_)

compiler/rustc_codegen_ssa/src/mir/operand.rs

@@ -140,7 +140,7 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
 
     pub(crate) fn from_const<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
         bx: &mut Bx,
-        val: mir::ConstValue<'tcx>,
+        val: mir::ConstValue,
         ty: Ty<'tcx>,
     ) -> Self {
         let layout = bx.layout_of(ty);
@@ -154,14 +154,11 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
                 OperandValue::Immediate(llval)
             }
             ConstValue::ZeroSized => return OperandRef::zero_sized(layout),
-            ConstValue::Slice { data, meta } => {
+            ConstValue::Slice { alloc_id, meta } => {
                 let BackendRepr::ScalarPair(a_scalar, _) = layout.backend_repr else {
                     bug!("from_const: invalid ScalarPair layout: {:#?}", layout);
                 };
-                let a = Scalar::from_pointer(
-                    Pointer::new(bx.tcx().reserve_and_set_memory_alloc(data).into(), Size::ZERO),
-                    &bx.tcx(),
-                );
+                let a = Scalar::from_pointer(Pointer::new(alloc_id.into(), Size::ZERO), &bx.tcx());
                 let a_llval = bx.scalar_to_backend(
                     a,
                     a_scalar,

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -288,7 +288,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         // valid ranges. For example, `char`s are passed as just `i32`, with no
         // way for LLVM to know that they're 0x10FFFF at most. Thus we assume
         // the range of the input value too, not just the output range.
-        assume_scalar_range(bx, imm, from_scalar, from_backend_ty);
+        assume_scalar_range(bx, imm, from_scalar, from_backend_ty, None);
 
         imm = match (from_scalar.primitive(), to_scalar.primitive()) {
             (Int(_, is_signed), Int(..)) => bx.intcast(imm, to_backend_ty, is_signed),
@@ -869,7 +869,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     let ltext = bx.zext(is_lt, bx.type_i8());
                     bx.unchecked_ssub(gtext, ltext)
                 } else {
-                    // These operations are those expected by `tests/codegen/integer-cmp.rs`,
+                    // These operations are those expected by `tests/codegen-llvm/integer-cmp.rs`,
                     // from <https://github.com/rust-lang/rust/pull/63767>.
                     let is_lt = bx.icmp(pred(mir::BinOp::Lt), lhs, rhs);
                     let is_ne = bx.icmp(pred(mir::BinOp::Ne), lhs, rhs);
@@ -1064,7 +1064,7 @@ pub(super) fn transmute_scalar<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     // That said, last time we tried removing this, it didn't actually help
     // the rustc-perf results, so might as well keep doing it
     // <https://github.com/rust-lang/rust/pull/135610#issuecomment-2599275182>
-    assume_scalar_range(bx, imm, from_scalar, from_backend_ty);
+    assume_scalar_range(bx, imm, from_scalar, from_backend_ty, Some(&to_scalar));
 
     imm = match (from_scalar.primitive(), to_scalar.primitive()) {
         (Int(..) | Float(_), Int(..) | Float(_)) => bx.bitcast(imm, to_backend_ty),
@@ -1092,22 +1092,42 @@ pub(super) fn transmute_scalar<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     // since it's never passed to something with parameter metadata (especially
     // after MIR inlining) so the only way to tell the backend about the
     // constraint that the `transmute` introduced is to `assume` it.
-    assume_scalar_range(bx, imm, to_scalar, to_backend_ty);
+    assume_scalar_range(bx, imm, to_scalar, to_backend_ty, Some(&from_scalar));
 
     imm = bx.to_immediate_scalar(imm, to_scalar);
     imm
 }
 
+/// Emits an `assume` call that `imm`'s value is within the known range of `scalar`.
+///
+/// If `known` is `Some`, only emits the assume if it's more specific than
+/// whatever is already known from the range of *that* scalar.
 fn assume_scalar_range<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     bx: &mut Bx,
     imm: Bx::Value,
     scalar: abi::Scalar,
     backend_ty: Bx::Type,
+    known: Option<&abi::Scalar>,
 ) {
-    if matches!(bx.cx().sess().opts.optimize, OptLevel::No) || scalar.is_always_valid(bx.cx()) {
+    if matches!(bx.cx().sess().opts.optimize, OptLevel::No) {
         return;
     }
 
+    match (scalar, known) {
+        (abi::Scalar::Union { .. }, _) => return,
+        (_, None) => {
+            if scalar.is_always_valid(bx.cx()) {
+                return;
+            }
+        }
+        (abi::Scalar::Initialized { valid_range, .. }, Some(known)) => {
+            let known_range = known.valid_range(bx.cx());
+            if valid_range.contains_range(known_range, scalar.size(bx.cx())) {
+                return;
+            }
+        }
+    }
+
     match scalar.primitive() {
         abi::Primitive::Int(..) => {
             let range = scalar.valid_range(bx.cx());

compiler/rustc_codegen_ssa/src/traits/write.rs

@@ -1,3 +1,5 @@
+use std::path::PathBuf;
+
 use rustc_ast::expand::autodiff_attrs::AutoDiffItem;
 use rustc_errors::{DiagCtxtHandle, FatalError};
 use rustc_middle::dep_graph::WorkProduct;
@@ -24,8 +26,9 @@ pub trait WriteBackendMethods: Clone + 'static {
     /// if necessary and running any further optimizations
     fn run_and_optimize_fat_lto(
         cgcx: &CodegenContext<Self>,
+        exported_symbols_for_lto: &[String],
+        each_linked_rlib_for_lto: &[PathBuf],
         modules: Vec<FatLtoInput<Self>>,
-        cached_modules: Vec<(SerializedModule<Self::ModuleBuffer>, WorkProduct)>,
         diff_fncs: Vec<AutoDiffItem>,
     ) -> Result<ModuleCodegen<Self::Module>, FatalError>;
     /// Performs thin LTO by performing necessary global analysis and returning two
@@ -33,6 +36,8 @@ pub trait WriteBackendMethods: Clone + 'static {
     /// can simply be copied over from the incr. comp. cache.
     fn run_thin_lto(
         cgcx: &CodegenContext<Self>,
+        exported_symbols_for_lto: &[String],
+        each_linked_rlib_for_lto: &[PathBuf],
         modules: Vec<(String, Self::ThinBuffer)>,
         cached_modules: Vec<(SerializedModule<Self::ModuleBuffer>, WorkProduct)>,
     ) -> Result<(Vec<ThinModule<Self>>, Vec<WorkProduct>), FatalError>;

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -152,7 +152,7 @@ pub(crate) fn mk_eval_cx_to_read_const_val<'tcx>(
 pub fn mk_eval_cx_for_const_val<'tcx>(
     tcx: TyCtxtAt<'tcx>,
     typing_env: ty::TypingEnv<'tcx>,
-    val: mir::ConstValue<'tcx>,
+    val: mir::ConstValue,
     ty: Ty<'tcx>,
 ) -> Option<(CompileTimeInterpCx<'tcx>, OpTy<'tcx>)> {
     let ecx = mk_eval_cx_to_read_const_val(tcx.tcx, tcx.span, typing_env, CanAccessMutGlobal::No);
@@ -172,7 +172,7 @@ pub(super) fn op_to_const<'tcx>(
     ecx: &CompileTimeInterpCx<'tcx>,
     op: &OpTy<'tcx>,
     for_diagnostics: bool,
-) -> ConstValue<'tcx> {
+) -> ConstValue {
     // Handle ZST consistently and early.
     if op.layout.is_zst() {
         return ConstValue::ZeroSized;
@@ -241,10 +241,9 @@ pub(super) fn op_to_const<'tcx>(
                 let (prov, offset) =
                     ptr.into_pointer_or_addr().expect(msg).prov_and_relative_offset();
                 let alloc_id = prov.alloc_id();
-                let data = ecx.tcx.global_alloc(alloc_id).unwrap_memory();
                 assert!(offset == abi::Size::ZERO, "{}", msg);
                 let meta = b.to_target_usize(ecx).expect(msg);
-                ConstValue::Slice { data, meta }
+                ConstValue::Slice { alloc_id, meta }
             }
             Immediate::Uninit => bug!("`Uninit` is not a valid value for {}", op.layout.ty),
         },
@@ -256,7 +255,7 @@ pub(crate) fn turn_into_const_value<'tcx>(
     tcx: TyCtxt<'tcx>,
     constant: ConstAlloc<'tcx>,
     key: ty::PseudoCanonicalInput<'tcx, GlobalId<'tcx>>,
-) -> ConstValue<'tcx> {
+) -> ConstValue {
     let cid = key.value;
     let def_id = cid.instance.def.def_id();
     let is_static = tcx.is_static(def_id);

compiler/rustc_const_eval/src/const_eval/mod.rs

@@ -28,7 +28,7 @@ const VALTREE_MAX_NODES: usize = 100000;
 #[instrument(skip(tcx), level = "debug")]
 pub(crate) fn try_destructure_mir_constant_for_user_output<'tcx>(
     tcx: TyCtxt<'tcx>,
-    val: mir::ConstValue<'tcx>,
+    val: mir::ConstValue,
     ty: Ty<'tcx>,
 ) -> Option<mir::DestructuredConstant<'tcx>> {
     let typing_env = ty::TypingEnv::fully_monomorphized();

compiler/rustc_const_eval/src/const_eval/valtrees.rs

@@ -259,7 +259,7 @@ pub fn valtree_to_const_value<'tcx>(
     tcx: TyCtxt<'tcx>,
     typing_env: ty::TypingEnv<'tcx>,
     cv: ty::Value<'tcx>,
-) -> mir::ConstValue<'tcx> {
+) -> mir::ConstValue {
     // Basic idea: We directly construct `Scalar` values from trivial `ValTree`s
     // (those for constants with type bool, int, uint, float or char).
     // For all other types we create an `MPlace` and fill that by walking

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -582,8 +582,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         span: Span,
         layout: Option<TyAndLayout<'tcx>>,
     ) -> InterpResult<'tcx, OpTy<'tcx, M::Provenance>> {
-        M::eval_mir_constant(self, *val, span, layout, |ecx, val, span, layout| {
-            let const_val = val.eval(*ecx.tcx, ecx.typing_env, span).map_err(|err| {
+        let const_val = val.eval(*self.tcx, self.typing_env, span).map_err(|err| {
                 if M::ALL_CONSTS_ARE_PRECHECKED {
                     match err {
                         ErrorHandled::TooGeneric(..) => {},
@@ -599,11 +598,10 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                         }
                     }
                 }
-                err.emit_note(*ecx.tcx);
+                err.emit_note(*self.tcx);
                 err
             })?;
-            ecx.const_val_to_op(const_val, val.ty(), layout)
-        })
+        self.const_val_to_op(const_val, val.ty(), layout)
     }
 
     #[must_use]

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -6,7 +6,7 @@ use std::assert_matches::assert_matches;
 
 use rustc_abi::{FieldIdx, HasDataLayout, Size};
 use rustc_apfloat::ieee::{Double, Half, Quad, Single};
-use rustc_middle::mir::interpret::{read_target_uint, write_target_uint};
+use rustc_middle::mir::interpret::{CTFE_ALLOC_SALT, read_target_uint, write_target_uint};
 use rustc_middle::mir::{self, BinOp, ConstValue, NonDivergingIntrinsic};
 use rustc_middle::ty::layout::TyAndLayout;
 use rustc_middle::ty::{Ty, TyCtxt};
@@ -17,17 +17,18 @@ use tracing::trace;
 use super::memory::MemoryKind;
 use super::util::ensure_monomorphic_enough;
 use super::{
-    Allocation, CheckInAllocMsg, ConstAllocation, ImmTy, InterpCx, InterpResult, Machine, OpTy,
-    PlaceTy, Pointer, PointerArithmetic, Provenance, Scalar, err_ub_custom, err_unsup_format,
-    interp_ok, throw_inval, throw_ub_custom, throw_ub_format,
+    AllocId, CheckInAllocMsg, ImmTy, InterpCx, InterpResult, Machine, OpTy, PlaceTy, Pointer,
+    PointerArithmetic, Provenance, Scalar, err_ub_custom, err_unsup_format, interp_ok, throw_inval,
+    throw_ub_custom, throw_ub_format,
 };
 use crate::fluent_generated as fluent;
 
 /// Directly returns an `Allocation` containing an absolute path representation of the given type.
-pub(crate) fn alloc_type_name<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ConstAllocation<'tcx> {
+pub(crate) fn alloc_type_name<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> (AllocId, u64) {
     let path = crate::util::type_name(tcx, ty);
-    let alloc = Allocation::from_bytes_byte_aligned_immutable(path.into_bytes(), ());
-    tcx.mk_const_alloc(alloc)
+    let bytes = path.into_bytes();
+    let len = bytes.len().try_into().unwrap();
+    (tcx.allocate_bytes_dedup(bytes, CTFE_ALLOC_SALT), len)
 }
 impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
     /// Generates a value of `TypeId` for `ty` in-place.
@@ -126,8 +127,8 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
             sym::type_name => {
                 let tp_ty = instance.args.type_at(0);
                 ensure_monomorphic_enough(tcx, tp_ty)?;
-                let alloc = alloc_type_name(tcx, tp_ty);
-                let val = ConstValue::Slice { data: alloc, meta: alloc.inner().size().bytes() };
+                let (alloc_id, meta) = alloc_type_name(tcx, tp_ty);
+                let val = ConstValue::Slice { alloc_id, meta };
                 let val = self.const_val_to_op(val, dest.layout.ty, Some(dest.layout))?;
                 self.copy_op(&val, dest)?;
             }

compiler/rustc_const_eval/src/interpret/machine.rs

@@ -12,7 +12,6 @@ use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::Ty;
 use rustc_middle::ty::layout::TyAndLayout;
 use rustc_middle::{mir, ty};
-use rustc_span::Span;
 use rustc_span::def_id::DefId;
 use rustc_target::callconv::FnAbi;
 
@@ -587,27 +586,6 @@ pub trait Machine<'tcx>: Sized {
         interp_ok(())
     }
 
-    /// Evaluate the given constant. The `eval` function will do all the required evaluation,
-    /// but this hook has the chance to do some pre/postprocessing.
-    #[inline(always)]
-    fn eval_mir_constant<F>(
-        ecx: &InterpCx<'tcx, Self>,
-        val: mir::Const<'tcx>,
-        span: Span,
-        layout: Option<TyAndLayout<'tcx>>,
-        eval: F,
-    ) -> InterpResult<'tcx, OpTy<'tcx, Self::Provenance>>
-    where
-        F: Fn(
-            &InterpCx<'tcx, Self>,
-            mir::Const<'tcx>,
-            Span,
-            Option<TyAndLayout<'tcx>>,
-        ) -> InterpResult<'tcx, OpTy<'tcx, Self::Provenance>>,
-    {
-        eval(ecx, val, span, layout)
-    }
-
     /// Returns the salt to be used for a deduplicated global alloation.
     /// If the allocation is for a function, the instance is provided as well
     /// (this lets Miri ensure unique addresses for some functions).

compiler/rustc_const_eval/src/interpret/memory.rs

@@ -1000,7 +1000,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         ptr: Pointer<Option<M::Provenance>>,
     ) -> InterpResult<'tcx, (Ty<'tcx>, u64)> {
         let (alloc_id, offset, _meta) = self.ptr_get_alloc_id(ptr, 0)?;
-        let GlobalAlloc::TypeId { ty } = self.tcx.global_alloc(alloc_id) else {
+        let Some(GlobalAlloc::TypeId { ty }) = self.tcx.try_get_global_alloc(alloc_id) else {
             throw_ub_format!("invalid `TypeId` value: not all bytes carry type id metadata")
         };
         interp_ok((ty, offset.bytes()))

compiler/rustc_const_eval/src/interpret/operand.rs

@@ -836,7 +836,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
 
     pub(crate) fn const_val_to_op(
         &self,
-        val_val: mir::ConstValue<'tcx>,
+        val_val: mir::ConstValue,
         ty: Ty<'tcx>,
         layout: Option<TyAndLayout<'tcx>>,
     ) -> InterpResult<'tcx, OpTy<'tcx, M::Provenance>> {
@@ -860,9 +860,8 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
             }
             mir::ConstValue::Scalar(x) => adjust_scalar(x)?.into(),
             mir::ConstValue::ZeroSized => Immediate::Uninit,
-            mir::ConstValue::Slice { data, meta } => {
+            mir::ConstValue::Slice { alloc_id, meta } => {
                 // This is const data, no mutation allowed.
-                let alloc_id = self.tcx.reserve_and_set_memory_alloc(data);
                 let ptr = Pointer::new(CtfeProvenance::from(alloc_id).as_immutable(), Size::ZERO);
                 Immediate::new_slice(self.global_root_pointer(ptr)?.into(), meta, self)
             }

compiler/rustc_const_eval/src/util/caller_location.rs

@@ -57,7 +57,7 @@ pub(crate) fn const_caller_location_provider(
     file: Symbol,
     line: u32,
     col: u32,
-) -> mir::ConstValue<'_> {
+) -> mir::ConstValue {
     trace!("const_caller_location: {}:{}:{}", file, line, col);
     let mut ecx = mk_eval_cx_to_read_const_val(
         tcx,

compiler/rustc_error_codes/src/error_codes/E0466.md

@@ -1,8 +1,10 @@
+#### Note: this error code is no longer emitted by the compiler.
+
 Macro import declaration was malformed.
 
 Erroneous code examples:
 
-```compile_fail,E0466
+```compile_fail
 #[macro_use(a_macro(another_macro))] // error: invalid import declaration
 extern crate core as some_crate;
 

compiler/rustc_expand/src/base.rs

@@ -1,3 +1,4 @@
+use std::any::Any;
 use std::default::Default;
 use std::iter;
 use std::path::Component::Prefix;
@@ -361,17 +362,13 @@ where
 }
 
 /// Represents a thing that maps token trees to Macro Results
-pub trait TTMacroExpander {
+pub trait TTMacroExpander: Any {
     fn expand<'cx>(
         &self,
         ecx: &'cx mut ExtCtxt<'_>,
         span: Span,
         input: TokenStream,
     ) -> MacroExpanderResult<'cx>;
-
-    fn get_unused_rule(&self, _rule_i: usize) -> Option<(&Ident, Span)> {
-        None
-    }
 }
 
 pub type MacroExpanderResult<'cx> = ExpandResult<Box<dyn MacResult + 'cx>, ()>;
@@ -379,7 +376,7 @@ pub type MacroExpanderResult<'cx> = ExpandResult<Box<dyn MacResult + 'cx>, ()>;
 pub type MacroExpanderFn =
     for<'cx> fn(&'cx mut ExtCtxt<'_>, Span, TokenStream) -> MacroExpanderResult<'cx>;
 
-impl<F> TTMacroExpander for F
+impl<F: 'static> TTMacroExpander for F
 where
     F: for<'cx> Fn(&'cx mut ExtCtxt<'_>, Span, TokenStream) -> MacroExpanderResult<'cx>,
 {

compiler/rustc_expand/src/lib.rs

@@ -22,7 +22,7 @@ mod placeholders;
 mod proc_macro_server;
 mod stats;
 
-pub use mbe::macro_rules::compile_declarative_macro;
+pub use mbe::macro_rules::{MacroRulesMacroExpander, compile_declarative_macro};
 pub mod base;
 pub mod config;
 pub mod expand;

compiler/rustc_expand/src/mbe/macro_rules.rs

@@ -128,7 +128,7 @@ pub(super) struct MacroRule {
     rhs: mbe::TokenTree,
 }
 
-struct MacroRulesMacroExpander {
+pub struct MacroRulesMacroExpander {
     node_id: NodeId,
     name: Ident,
     span: Span,
@@ -136,6 +136,14 @@ struct MacroRulesMacroExpander {
     rules: Vec<MacroRule>,
 }
 
+impl MacroRulesMacroExpander {
+    pub fn get_unused_rule(&self, rule_i: usize) -> Option<(&Ident, Span)> {
+        // If the rhs contains an invocation like `compile_error!`, don't report it as unused.
+        let rule = &self.rules[rule_i];
+        if has_compile_error_macro(&rule.rhs) { None } else { Some((&self.name, rule.lhs_span)) }
+    }
+}
+
 impl TTMacroExpander for MacroRulesMacroExpander {
     fn expand<'cx>(
         &self,
@@ -154,12 +162,6 @@ impl TTMacroExpander for MacroRulesMacroExpander {
             &self.rules,
         ))
     }
-
-    fn get_unused_rule(&self, rule_i: usize) -> Option<(&Ident, Span)> {
-        // If the rhs contains an invocation like `compile_error!`, don't report it as unused.
-        let rule = &self.rules[rule_i];
-        if has_compile_error_macro(&rule.rhs) { None } else { Some((&self.name, rule.lhs_span)) }
-    }
 }
 
 struct DummyExpander(ErrorGuaranteed);

compiler/rustc_hir/src/hir.rs

@@ -1302,6 +1302,7 @@ impl AttributeExt for Attribute {
             // FIXME: should not be needed anymore when all attrs are parsed
             Attribute::Parsed(AttributeKind::Deprecation { span, .. }) => *span,
             Attribute::Parsed(AttributeKind::DocComment { span, .. }) => *span,
+            Attribute::Parsed(AttributeKind::MacroUse { span, .. }) => *span,
             Attribute::Parsed(AttributeKind::MayDangle(span)) => *span,
             Attribute::Parsed(AttributeKind::Ignore { span, .. }) => *span,
             Attribute::Parsed(AttributeKind::AutomaticallyDerived(span)) => *span,

compiler/rustc_hir_analysis/src/check/check.rs

@@ -1642,20 +1642,40 @@ fn check_enum(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 
     if def.repr().int.is_none() {
         let is_unit = |var: &ty::VariantDef| matches!(var.ctor_kind(), Some(CtorKind::Const));
-        let has_disr = |var: &ty::VariantDef| matches!(var.discr, ty::VariantDiscr::Explicit(_));
+        let get_disr = |var: &ty::VariantDef| match var.discr {
+            ty::VariantDiscr::Explicit(disr) => Some(disr),
+            ty::VariantDiscr::Relative(_) => None,
+        };
 
-        let has_non_units = def.variants().iter().any(|var| !is_unit(var));
-        let disr_units = def.variants().iter().any(|var| is_unit(var) && has_disr(var));
-        let disr_non_unit = def.variants().iter().any(|var| !is_unit(var) && has_disr(var));
+        let non_unit = def.variants().iter().find(|var| !is_unit(var));
+        let disr_unit =
+            def.variants().iter().filter(|var| is_unit(var)).find_map(|var| get_disr(var));
+        let disr_non_unit =
+            def.variants().iter().filter(|var| !is_unit(var)).find_map(|var| get_disr(var));
 
-        if disr_non_unit || (disr_units && has_non_units) {
-            struct_span_code_err!(
+        if disr_non_unit.is_some() || (disr_unit.is_some() && non_unit.is_some()) {
+            let mut err = struct_span_code_err!(
                 tcx.dcx(),
                 tcx.def_span(def_id),
                 E0732,
-                "`#[repr(inttype)]` must be specified"
-            )
-            .emit();
+                "`#[repr(inttype)]` must be specified for enums with explicit discriminants and non-unit variants"
+            );
+            if let Some(disr_non_unit) = disr_non_unit {
+                err.span_label(
+                    tcx.def_span(disr_non_unit),
+                    "explicit discriminant on non-unit variant specified here",
+                );
+            } else {
+                err.span_label(
+                    tcx.def_span(disr_unit.unwrap()),
+                    "explicit discriminant specified here",
+                );
+                err.span_label(
+                    tcx.def_span(non_unit.unwrap().def_id),
+                    "non-unit discriminant declared here",
+                );
+            }
+            err.emit();
         }
     }
 

compiler/rustc_hir_analysis/src/check_unused.rs

@@ -18,7 +18,7 @@ pub(super) fn check_unused_traits(tcx: TyCtxt<'_>, (): ()) {
         used_trait_imports.extend_unord(imports.items().copied());
     }
 
-    for &id in tcx.maybe_unused_trait_imports(()) {
+    for &id in tcx.resolutions(()).maybe_unused_trait_imports.iter() {
         debug_assert_eq!(tcx.def_kind(id), DefKind::Use);
         if tcx.visibility(id).is_public() {
             continue;

compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs

@@ -447,17 +447,30 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     fn maybe_suggest_assoc_ty_bound(&self, self_ty: &hir::Ty<'_>, diag: &mut Diag<'_>) {
         let mut parents = self.tcx().hir_parent_iter(self_ty.hir_id);
 
-        if let Some((_, hir::Node::AssocItemConstraint(constraint))) = parents.next()
+        if let Some((c_hir_id, hir::Node::AssocItemConstraint(constraint))) = parents.next()
             && let Some(obj_ty) = constraint.ty()
+            && let Some((_, hir::Node::TraitRef(trait_ref))) = parents.next()
         {
-            if let Some((_, hir::Node::TraitRef(..))) = parents.next()
-                && let Some((_, hir::Node::Ty(ty))) = parents.next()
+            if let Some((_, hir::Node::Ty(ty))) = parents.next()
                 && let hir::TyKind::TraitObject(..) = ty.kind
             {
                 // Assoc ty bounds aren't permitted inside trait object types.
                 return;
             }
 
+            if trait_ref
+                .path
+                .segments
+                .iter()
+                .find_map(|seg| {
+                    seg.args.filter(|args| args.constraints.iter().any(|c| c.hir_id == c_hir_id))
+                })
+                .is_none_or(|args| args.parenthesized != hir::GenericArgsParentheses::No)
+            {
+                // Only consider angle-bracketed args (where we have a `=` to replace with `:`).
+                return;
+            }
+
             let lo = if constraint.gen_args.span_ext.is_dummy() {
                 constraint.ident.span
             } else {

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -1302,8 +1302,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 None => ".clone()".to_string(),
             };
 
+            let span = expr.span.find_oldest_ancestor_in_same_ctxt().shrink_to_hi();
+
             diag.span_suggestion_verbose(
-                expr.span.shrink_to_hi(),
+                span,
                 "consider using clone here",
                 suggestion,
                 Applicability::MachineApplicable,

compiler/rustc_hir_typeck/src/upvar.rs

@@ -1047,7 +1047,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             }
                         }
                     }
-                    lint.note("for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/disjoint-capture-in-closures.html>");
+                    lint.note("for more information, see <https://doc.rust-lang.org/edition-guide/rust-2021/disjoint-capture-in-closures.html>");
 
                     let diagnostic_msg = format!(
                         "add a dummy let to cause {migrated_variables_concat} to be fully captured"

compiler/rustc_lint/messages.ftl

@@ -593,7 +593,7 @@ lint_non_camel_case_type = {$sort} `{$name}` should have an upper camel case nam
 
 lint_non_fmt_panic = panic message is not a string literal
     .note = this usage of `{$name}!()` is deprecated; it will be a hard error in Rust 2021
-    .more_info_note = for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/panic-macro-consistency.html>
+    .more_info_note = for more information, see <https://doc.rust-lang.org/edition-guide/rust-2021/panic-macro-consistency.html>
     .supports_fmt_note = the `{$name}!()` macro supports formatting, so there's no need for the `format!()` macro here
     .supports_fmt_suggestion = remove the `format!(..)` macro call
     .display_suggestion = add a "{"{"}{"}"}" format string to `Display` the message

compiler/rustc_lint/src/builtin.rs

@@ -1654,7 +1654,7 @@ declare_lint! {
     "`...` range patterns are deprecated",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2021/warnings-promoted-to-error.html>",
     };
 }
 
@@ -1835,7 +1835,7 @@ declare_lint! {
     "detects edition keywords being used as an identifier",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2024),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/gen-keyword.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2024/gen-keyword.html>",
     };
 }
 

compiler/rustc_lint/src/if_let_rescope.rs

@@ -87,7 +87,7 @@ declare_lint! {
     rewriting in `match` is an option to preserve the semantics up to Edition 2021",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2024),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/temporary-if-let-scope.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2024/temporary-if-let-scope.html>",
     };
 }
 

compiler/rustc_lint/src/impl_trait_overcaptures.rs

@@ -71,7 +71,7 @@ declare_lint! {
     "`impl Trait` will capture more lifetimes than possibly intended in edition 2024",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2024),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/rpit-lifetime-capture.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2024/rpit-lifetime-capture.html>",
     };
 }
 

compiler/rustc_lint/src/macro_expr_fragment_specifier_2024_migration.rs

@@ -65,7 +65,7 @@ declare_lint! {
     /// to ensure the macros implement the desired behavior.
     ///
     /// [editions]: https://doc.rust-lang.org/edition-guide/
-    /// [macro matcher fragment specifiers]: https://doc.rust-lang.org/nightly/edition-guide/rust-2024/macro-fragment-specifiers.html
+    /// [macro matcher fragment specifiers]: https://doc.rust-lang.org/edition-guide/rust-2024/macro-fragment-specifiers.html
     /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
     pub EDITION_2024_EXPR_FRAGMENT_SPECIFIER,
     Allow,
@@ -73,7 +73,7 @@ declare_lint! {
     To keep the existing behavior, use the `expr_2021` fragment specifier.",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2024),
-        reference: "Migration Guide <https://doc.rust-lang.org/nightly/edition-guide/rust-2024/macro-fragment-specifiers.html>",
+        reference: "Migration Guide <https://doc.rust-lang.org/edition-guide/rust-2024/macro-fragment-specifiers.html>",
     };
 }
 

compiler/rustc_lint/src/shadowed_into_iter.rs

@@ -32,7 +32,7 @@ declare_lint! {
     "detects calling `into_iter` on arrays in Rust 2015 and 2018",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2021),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/IntoIterator-for-arrays.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2021/IntoIterator-for-arrays.html>",
     };
 }
 
@@ -61,7 +61,7 @@ declare_lint! {
     "detects calling `into_iter` on boxed slices in Rust 2015, 2018, and 2021",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2024),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/intoiterator-box-slice.html>"
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2024/intoiterator-box-slice.html>"
     };
 }
 

compiler/rustc_lint/src/static_mut_refs.rs

@@ -54,7 +54,7 @@ declare_lint! {
     "creating a shared reference to mutable static",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2024),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/static-mut-references.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2024/static-mut-references.html>",
         explain_reason: false,
     };
     @edition Edition2024 => Deny;

compiler/rustc_lint_defs/src/builtin.rs

@@ -1814,7 +1814,7 @@ declare_lint! {
     "suggest using `dyn Trait` for trait objects",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2021/warnings-promoted-to-error.html>",
     };
 }
 
@@ -2472,7 +2472,7 @@ declare_lint! {
     "unsafe operations in unsafe functions without an explicit unsafe block are deprecated",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2024),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/unsafe-op-in-unsafe-fn.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2024/unsafe-op-in-unsafe-fn.html>",
         explain_reason: false
     };
     @edition Edition2024 => Warn;
@@ -3445,7 +3445,7 @@ declare_lint! {
     "detects usage of old versions of or-patterns",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/or-patterns-macro-rules.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2021/or-patterns-macro-rules.html>",
     };
 }
 
@@ -3494,7 +3494,7 @@ declare_lint! {
         prelude in future editions",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/prelude.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2021/prelude.html>",
     };
 }
 
@@ -3534,7 +3534,7 @@ declare_lint! {
         prelude in future editions",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2024),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/prelude.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2024/prelude.html>",
     };
 }
 
@@ -3571,7 +3571,7 @@ declare_lint! {
     "identifiers that will be parsed as a prefix in Rust 2021",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/reserving-syntax.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2021/reserving-syntax.html>",
     };
     crate_level_only
 }
@@ -4100,7 +4100,7 @@ declare_lint! {
     "never type fallback affecting unsafe function calls",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionAndFutureReleaseSemanticsChange(Edition::Edition2024),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/never-type-fallback.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2024/never-type-fallback.html>",
         report_in_deps: true,
     };
     @edition Edition2024 => Deny;
@@ -4155,7 +4155,7 @@ declare_lint! {
     "never type fallback affecting unsafe function calls",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionAndFutureReleaseError(Edition::Edition2024),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/never-type-fallback.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2024/never-type-fallback.html>",
         report_in_deps: true,
     };
     report_in_external_macro
@@ -4740,7 +4740,7 @@ declare_lint! {
     "detects unsafe functions being used as safe functions",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2024),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/newly-unsafe-functions.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2024/newly-unsafe-functions.html>",
     };
 }
 
@@ -4776,7 +4776,7 @@ declare_lint! {
     "detects missing unsafe keyword on extern declarations",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2024),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/unsafe-extern.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2024/unsafe-extern.html>",
     };
 }
 
@@ -4817,7 +4817,7 @@ declare_lint! {
     "detects unsafe attributes outside of unsafe",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2024),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/unsafe-attributes.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2024/unsafe-attributes.html>",
     };
 }
 
@@ -5014,7 +5014,7 @@ declare_lint! {
     "Detect and warn on significant change in drop order in tail expression location",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2024),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/temporary-tail-expr-scope.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2024/temporary-tail-expr-scope.html>",
     };
 }
 
@@ -5053,7 +5053,7 @@ declare_lint! {
     "will be parsed as a guarded string in Rust 2024",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2024),
-        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2024/reserved-syntax.html>",
+        reference: "<https://doc.rust-lang.org/edition-guide/rust-2024/reserved-syntax.html>",
     };
     crate_level_only
 }

compiler/rustc_macros/src/lib.rs

@@ -21,6 +21,7 @@ mod symbols;
 mod try_from;
 mod type_foldable;
 mod type_visitable;
+mod visitable;
 
 // Reads the rust version (e.g. "1.75.0") from the CFG_RELEASE env var and
 // produces a `RustcVersion` literal containing that version (e.g.
@@ -101,6 +102,16 @@ decl_derive!(
     /// visited (and its type is not required to implement `TypeVisitable`).
     type_visitable::type_visitable_derive
 );
+decl_derive!(
+    [Walkable, attributes(visitable)] =>
+    /// Derives `Walkable` for the annotated `struct` or `enum` (`union` is not supported).
+    ///
+    /// Each field of the struct or enum variant will be visited in definition order, using the
+    /// `Walkable` implementation for its type. However, if a field of a struct or an enum
+    /// variant is annotated with `#[visitable(ignore)]` then that field will not be
+    /// visited (and its type is not required to implement `Walkable`).
+    visitable::visitable_derive
+);
 decl_derive!([Lift, attributes(lift)] => lift::lift_derive);
 decl_derive!(
     [Diagnostic, attributes(

compiler/rustc_macros/src/visitable.rs

@@ -0,0 +1,82 @@
+use quote::quote;
+use synstructure::BindingInfo;
+
+pub(super) fn visitable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream {
+    if let syn::Data::Union(_) = s.ast().data {
+        panic!("cannot derive on union")
+    }
+
+    let has_attr = |bind: &BindingInfo<'_>, name| {
+        let mut found = false;
+        bind.ast().attrs.iter().for_each(|attr| {
+            if !attr.path().is_ident("visitable") {
+                return;
+            }
+            let _ = attr.parse_nested_meta(|nested| {
+                if nested.path.is_ident(name) {
+                    found = true;
+                }
+                Ok(())
+            });
+        });
+        found
+    };
+
+    let get_attr = |bind: &BindingInfo<'_>, name: &str| {
+        let mut content = None;
+        bind.ast().attrs.iter().for_each(|attr| {
+            if !attr.path().is_ident("visitable") {
+                return;
+            }
+            let _ = attr.parse_nested_meta(|nested| {
+                if nested.path.is_ident(name) {
+                    let value = nested.value()?;
+                    let value = value.parse()?;
+                    content = Some(value);
+                }
+                Ok(())
+            });
+        });
+        content
+    };
+
+    s.add_bounds(synstructure::AddBounds::Generics);
+    s.bind_with(|_| synstructure::BindStyle::Ref);
+    let ref_visit = s.each(|bind| {
+        let extra = get_attr(bind, "extra").unwrap_or(quote! {});
+        if has_attr(bind, "ignore") {
+            quote! {}
+        } else {
+            quote! { rustc_ast_ir::try_visit!(crate::visit::Visitable::visit(#bind, __visitor, (#extra))) }
+        }
+    });
+
+    s.bind_with(|_| synstructure::BindStyle::RefMut);
+    let mut_visit = s.each(|bind| {
+        let extra = get_attr(bind, "extra").unwrap_or(quote! {});
+        if has_attr(bind, "ignore") {
+            quote! {}
+        } else {
+            quote! { crate::mut_visit::MutVisitable::visit_mut(#bind, __visitor, (#extra)) }
+        }
+    });
+
+    s.gen_impl(quote! {
+        gen impl<'__ast, __V> crate::visit::Walkable<'__ast, __V> for @Self
+            where __V: crate::visit::Visitor<'__ast>,
+        {
+            fn walk_ref(&'__ast self, __visitor: &mut __V) -> __V::Result {
+                match *self { #ref_visit }
+                <__V::Result as rustc_ast_ir::visit::VisitorResult>::output()
+            }
+        }
+
+        gen impl<__V> crate::mut_visit::MutWalkable<__V> for @Self
+            where __V: crate::mut_visit::MutVisitor,
+        {
+            fn walk_mut(&mut self, __visitor: &mut __V) {
+                match *self { #mut_visit }
+            }
+        }
+    })
+}

compiler/rustc_metadata/messages.ftl

@@ -330,3 +330,6 @@ metadata_wasm_import_form =
 
 metadata_whole_archive_needs_static =
     linking modifier `whole-archive` is only compatible with `static` linking kind
+
+metadata_raw_dylib_malformed =
+    link name must be well-formed if link kind is `raw-dylib`

compiler/rustc_metadata/src/errors.rs

@@ -815,3 +815,10 @@ pub struct AsyncDropTypesInDependency {
     pub extern_crate: Symbol,
     pub local_crate: Symbol,
 }
+
+#[derive(Diagnostic)]
+#[diag(metadata_raw_dylib_malformed)]
+pub struct RawDylibMalformed {
+    #[primary_span]
+    pub span: Span,
+}

compiler/rustc_metadata/src/native_libs.rs

@@ -700,8 +700,21 @@ impl<'tcx> Collector<'tcx> {
             .link_ordinal
             .map_or(import_name_type, |ord| Some(PeImportNameType::Ordinal(ord)));
 
+        let name = codegen_fn_attrs.link_name.unwrap_or_else(|| self.tcx.item_name(item));
+
+        if self.tcx.sess.target.binary_format == BinaryFormat::Elf {
+            let name = name.as_str();
+            if name.contains('\0') {
+                self.tcx.dcx().emit_err(errors::RawDylibMalformed { span });
+            } else if let Some((left, right)) = name.split_once('@')
+                && (left.is_empty() || right.is_empty() || right.contains('@'))
+            {
+                self.tcx.dcx().emit_err(errors::RawDylibMalformed { span });
+            }
+        }
+
         DllImport {
-            name: codegen_fn_attrs.link_name.unwrap_or_else(|| self.tcx.item_name(item)),
+            name,
             import_name_type,
             calling_convention,
             span,

compiler/rustc_middle/src/hooks/mod.rs

@@ -50,10 +50,10 @@ macro_rules! declare_hooks {
 declare_hooks! {
     /// Tries to destructure an `mir::Const` ADT or array into its variant index
     /// and its field values. This should only be used for pretty printing.
-    hook try_destructure_mir_constant_for_user_output(val: mir::ConstValue<'tcx>, ty: Ty<'tcx>) -> Option<mir::DestructuredConstant<'tcx>>;
+    hook try_destructure_mir_constant_for_user_output(val: mir::ConstValue, ty: Ty<'tcx>) -> Option<mir::DestructuredConstant<'tcx>>;
 
     /// Getting a &core::panic::Location referring to a span.
-    hook const_caller_location(file: rustc_span::Symbol, line: u32, col: u32) -> mir::ConstValue<'tcx>;
+    hook const_caller_location(file: rustc_span::Symbol, line: u32, col: u32) -> mir::ConstValue;
 
     /// Returns `true` if this def is a function-like thing that is eligible for
     /// coverage instrumentation under `-Cinstrument-coverage`.

compiler/rustc_middle/src/mir/consts.rs

@@ -9,9 +9,7 @@ use rustc_span::{DUMMY_SP, Span, Symbol};
 use rustc_type_ir::TypeVisitableExt;
 
 use super::interpret::ReportedErrorInfo;
-use crate::mir::interpret::{
-    AllocId, AllocRange, ConstAllocation, ErrorHandled, GlobalAlloc, Scalar, alloc_range,
-};
+use crate::mir::interpret::{AllocId, AllocRange, ErrorHandled, GlobalAlloc, Scalar, alloc_range};
 use crate::mir::{Promoted, pretty_print_const_value};
 use crate::ty::print::{pretty_print_const, with_no_trimmed_paths};
 use crate::ty::{self, ConstKind, GenericArgsRef, ScalarInt, Ty, TyCtxt};
@@ -33,8 +31,8 @@ pub struct ConstAlloc<'tcx> {
 /// Represents a constant value in Rust. `Scalar` and `Slice` are optimizations for
 /// array length computations, enum discriminants and the pattern matching logic.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Hash)]
-#[derive(HashStable, Lift)]
-pub enum ConstValue<'tcx> {
+#[derive(HashStable)]
+pub enum ConstValue {
     /// Used for types with `layout::abi::Scalar` ABI.
     ///
     /// Not using the enum `Value` to encode that this must not be `Uninit`.
@@ -52,7 +50,7 @@ pub enum ConstValue<'tcx> {
     Slice {
         /// The allocation storing the slice contents.
         /// This always points to the beginning of the allocation.
-        data: ConstAllocation<'tcx>,
+        alloc_id: AllocId,
         /// The metadata field of the reference.
         /// This is a "target usize", so we use `u64` as in the interpreter.
         meta: u64,
@@ -75,9 +73,9 @@ pub enum ConstValue<'tcx> {
 }
 
 #[cfg(target_pointer_width = "64")]
-rustc_data_structures::static_assert_size!(ConstValue<'_>, 24);
+rustc_data_structures::static_assert_size!(ConstValue, 24);
 
-impl<'tcx> ConstValue<'tcx> {
+impl ConstValue {
     #[inline]
     pub fn try_to_scalar(&self) -> Option<Scalar> {
         match *self {
@@ -98,11 +96,11 @@ impl<'tcx> ConstValue<'tcx> {
         self.try_to_scalar_int()?.try_into().ok()
     }
 
-    pub fn try_to_target_usize(&self, tcx: TyCtxt<'tcx>) -> Option<u64> {
+    pub fn try_to_target_usize(&self, tcx: TyCtxt<'_>) -> Option<u64> {
         Some(self.try_to_scalar_int()?.to_target_usize(tcx))
     }
 
-    pub fn try_to_bits_for_ty(
+    pub fn try_to_bits_for_ty<'tcx>(
         &self,
         tcx: TyCtxt<'tcx>,
         typing_env: ty::TypingEnv<'tcx>,
@@ -132,12 +130,15 @@ impl<'tcx> ConstValue<'tcx> {
     }
 
     /// Must only be called on constants of type `&str` or `&[u8]`!
-    pub fn try_get_slice_bytes_for_diagnostics(&self, tcx: TyCtxt<'tcx>) -> Option<&'tcx [u8]> {
-        let (data, start, end) = match self {
+    pub fn try_get_slice_bytes_for_diagnostics<'tcx>(
+        &self,
+        tcx: TyCtxt<'tcx>,
+    ) -> Option<&'tcx [u8]> {
+        let (alloc_id, start, len) = match self {
             ConstValue::Scalar(_) | ConstValue::ZeroSized => {
                 bug!("`try_get_slice_bytes` on non-slice constant")
             }
-            &ConstValue::Slice { data, meta } => (data, 0, meta),
+            &ConstValue::Slice { alloc_id, meta } => (alloc_id, 0, meta),
             &ConstValue::Indirect { alloc_id, offset } => {
                 // The reference itself is stored behind an indirection.
                 // Load the reference, and then load the actual slice contents.
@@ -170,26 +171,29 @@ impl<'tcx> ConstValue<'tcx> {
                 // Non-empty slice, must have memory. We know this is a relative pointer.
                 let (inner_prov, offset) =
                     ptr.into_pointer_or_addr().ok()?.prov_and_relative_offset();
-                let data = tcx.global_alloc(inner_prov.alloc_id()).unwrap_memory();
-                (data, offset.bytes(), offset.bytes() + len)
+                (inner_prov.alloc_id(), offset.bytes(), len)
             }
         };
 
+        let data = tcx.global_alloc(alloc_id).unwrap_memory();
+
         // This is for diagnostics only, so we are okay to use `inspect_with_uninit_and_ptr_outside_interpreter`.
         let start = start.try_into().unwrap();
-        let end = end.try_into().unwrap();
+        let end = start + usize::try_from(len).unwrap();
         Some(data.inner().inspect_with_uninit_and_ptr_outside_interpreter(start..end))
     }
 
     /// Check if a constant may contain provenance information. This is used by MIR opts.
     /// Can return `true` even if there is no provenance.
-    pub fn may_have_provenance(&self, tcx: TyCtxt<'tcx>, size: Size) -> bool {
+    pub fn may_have_provenance(&self, tcx: TyCtxt<'_>, size: Size) -> bool {
         match *self {
             ConstValue::ZeroSized | ConstValue::Scalar(Scalar::Int(_)) => return false,
             ConstValue::Scalar(Scalar::Ptr(..)) => return true,
             // It's hard to find out the part of the allocation we point to;
             // just conservatively check everything.
-            ConstValue::Slice { data, meta: _ } => !data.inner().provenance().ptrs().is_empty(),
+            ConstValue::Slice { alloc_id, meta: _ } => {
+                !tcx.global_alloc(alloc_id).unwrap_memory().inner().provenance().ptrs().is_empty()
+            }
             ConstValue::Indirect { alloc_id, offset } => !tcx
                 .global_alloc(alloc_id)
                 .unwrap_memory()
@@ -200,7 +204,7 @@ impl<'tcx> ConstValue<'tcx> {
     }
 
     /// Check if a constant only contains uninitialized bytes.
-    pub fn all_bytes_uninit(&self, tcx: TyCtxt<'tcx>) -> bool {
+    pub fn all_bytes_uninit(&self, tcx: TyCtxt<'_>) -> bool {
         let ConstValue::Indirect { alloc_id, .. } = self else {
             return false;
         };
@@ -247,7 +251,7 @@ pub enum Const<'tcx> {
 
     /// This constant cannot go back into the type system, as it represents
     /// something the type system cannot handle (e.g. pointers).
-    Val(ConstValue<'tcx>, Ty<'tcx>),
+    Val(ConstValue, Ty<'tcx>),
 }
 
 impl<'tcx> Const<'tcx> {
@@ -343,7 +347,7 @@ impl<'tcx> Const<'tcx> {
         tcx: TyCtxt<'tcx>,
         typing_env: ty::TypingEnv<'tcx>,
         span: Span,
-    ) -> Result<ConstValue<'tcx>, ErrorHandled> {
+    ) -> Result<ConstValue, ErrorHandled> {
         match self {
             Const::Ty(_, c) => {
                 if c.has_non_region_param() {
@@ -440,7 +444,7 @@ impl<'tcx> Const<'tcx> {
     }
 
     #[inline]
-    pub fn from_value(val: ConstValue<'tcx>, ty: Ty<'tcx>) -> Self {
+    pub fn from_value(val: ConstValue, ty: Ty<'tcx>) -> Self {
         Self::Val(val, ty)
     }
 
@@ -487,9 +491,8 @@ impl<'tcx> Const<'tcx> {
     /// taking into account even pointer identity tests.
     pub fn is_deterministic(&self) -> bool {
         // Some constants may generate fresh allocations for pointers they contain,
-        // so using the same constant twice can yield two different results:
-        // - valtrees purposefully generate new allocations
-        // - ConstValue::Slice also generate new allocations
+        // so using the same constant twice can yield two different results.
+        // Notably, valtrees purposefully generate new allocations.
         match self {
             Const::Ty(_, c) => match c.kind() {
                 ty::ConstKind::Param(..) => true,
@@ -507,11 +510,11 @@ impl<'tcx> Const<'tcx> {
                 | ty::ConstKind::Placeholder(..) => bug!(),
             },
             Const::Unevaluated(..) => false,
-            // If the same slice appears twice in the MIR, we cannot guarantee that we will
-            // give the same `AllocId` to the data.
-            Const::Val(ConstValue::Slice { .. }, _) => false,
             Const::Val(
-                ConstValue::ZeroSized | ConstValue::Scalar(_) | ConstValue::Indirect { .. },
+                ConstValue::Slice { .. }
+                | ConstValue::ZeroSized
+                | ConstValue::Scalar(_)
+                | ConstValue::Indirect { .. },
                 _,
             ) => true,
         }
@@ -574,7 +577,7 @@ impl<'tcx> Display for Const<'tcx> {
 /// Const-related utilities
 
 impl<'tcx> TyCtxt<'tcx> {
-    pub fn span_as_caller_location(self, span: Span) -> ConstValue<'tcx> {
+    pub fn span_as_caller_location(self, span: Span) -> ConstValue {
         let topmost = span.ctxt().outer_expn().expansion_cause().unwrap_or(span);
         let caller = self.sess.source_map().lookup_char_pos(topmost.lo());
         self.const_caller_location(

compiler/rustc_middle/src/mir/interpret/error.rs

@@ -137,7 +137,7 @@ impl<'tcx> ValTreeCreationError<'tcx> {
 
 pub type EvalToAllocationRawResult<'tcx> = Result<ConstAlloc<'tcx>, ErrorHandled>;
 pub type EvalStaticInitializerRawResult<'tcx> = Result<ConstAllocation<'tcx>, ErrorHandled>;
-pub type EvalToConstValueResult<'tcx> = Result<ConstValue<'tcx>, ErrorHandled>;
+pub type EvalToConstValueResult<'tcx> = Result<ConstValue, ErrorHandled>;
 pub type EvalToValTreeResult<'tcx> = Result<ValTree<'tcx>, ValTreeCreationError<'tcx>>;
 
 #[cfg(target_pointer_width = "64")]

compiler/rustc_middle/src/mir/mono.rs

@@ -143,10 +143,8 @@ impl<'tcx> MonoItem<'tcx> {
         };
 
         // Similarly, the executable entrypoint must be instantiated exactly once.
-        if let Some((entry_def_id, _)) = tcx.entry_fn(()) {
-            if instance.def_id() == entry_def_id {
-                return InstantiationMode::GloballyShared { may_conflict: false };
-            }
+        if tcx.is_entrypoint(instance.def_id()) {
+            return InstantiationMode::GloballyShared { may_conflict: false };
         }
 
         // If the function is #[naked] or contains any other attribute that requires exactly-once

compiler/rustc_middle/src/mir/pretty.rs

@@ -1465,7 +1465,7 @@ impl<'tcx> Visitor<'tcx> for ExtraComments<'tcx> {
                 self.push(&format!("+ user_ty: {user_ty:?}"));
             }
 
-            let fmt_val = |val: ConstValue<'tcx>, ty: Ty<'tcx>| {
+            let fmt_val = |val: ConstValue, ty: Ty<'tcx>| {
                 let tcx = self.tcx;
                 rustc_data_structures::make_display(move |fmt| {
                     pretty_print_const_value_tcx(tcx, val, ty, fmt)
@@ -1562,16 +1562,12 @@ pub fn write_allocations<'tcx>(
         alloc.inner().provenance().ptrs().values().map(|p| p.alloc_id())
     }
 
-    fn alloc_id_from_const_val(val: ConstValue<'_>) -> Option<AllocId> {
+    fn alloc_id_from_const_val(val: ConstValue) -> Option<AllocId> {
         match val {
             ConstValue::Scalar(interpret::Scalar::Ptr(ptr, _)) => Some(ptr.provenance.alloc_id()),
             ConstValue::Scalar(interpret::Scalar::Int { .. }) => None,
             ConstValue::ZeroSized => None,
-            ConstValue::Slice { .. } => {
-                // `u8`/`str` slices, shouldn't contain pointers that we want to print.
-                None
-            }
-            ConstValue::Indirect { alloc_id, .. } => {
+            ConstValue::Slice { alloc_id, .. } | ConstValue::Indirect { alloc_id, .. } => {
                 // FIXME: we don't actually want to print all of these, since some are printed nicely directly as values inline in MIR.
                 // Really we'd want `pretty_print_const_value` to decide which allocations to print, instead of having a separate visitor.
                 Some(alloc_id)
@@ -1885,7 +1881,7 @@ fn pretty_print_byte_str(fmt: &mut Formatter<'_>, byte_str: &[u8]) -> fmt::Resul
 fn comma_sep<'tcx>(
     tcx: TyCtxt<'tcx>,
     fmt: &mut Formatter<'_>,
-    elems: Vec<(ConstValue<'tcx>, Ty<'tcx>)>,
+    elems: Vec<(ConstValue, Ty<'tcx>)>,
 ) -> fmt::Result {
     let mut first = true;
     for (ct, ty) in elems {
@@ -1900,7 +1896,7 @@ fn comma_sep<'tcx>(
 
 fn pretty_print_const_value_tcx<'tcx>(
     tcx: TyCtxt<'tcx>,
-    ct: ConstValue<'tcx>,
+    ct: ConstValue,
     ty: Ty<'tcx>,
     fmt: &mut Formatter<'_>,
 ) -> fmt::Result {
@@ -1947,7 +1943,7 @@ fn pretty_print_const_value_tcx<'tcx>(
             let ct = tcx.lift(ct).unwrap();
             let ty = tcx.lift(ty).unwrap();
             if let Some(contents) = tcx.try_destructure_mir_constant_for_user_output(ct, ty) {
-                let fields: Vec<(ConstValue<'_>, Ty<'_>)> = contents.fields.to_vec();
+                let fields: Vec<(ConstValue, Ty<'_>)> = contents.fields.to_vec();
                 match *ty.kind() {
                     ty::Array(..) => {
                         fmt.write_str("[")?;
@@ -2028,7 +2024,7 @@ fn pretty_print_const_value_tcx<'tcx>(
 }
 
 pub(crate) fn pretty_print_const_value<'tcx>(
-    ct: ConstValue<'tcx>,
+    ct: ConstValue,
     ty: Ty<'tcx>,
     fmt: &mut Formatter<'_>,
 ) -> fmt::Result {

compiler/rustc_middle/src/mir/query.rs

@@ -173,5 +173,5 @@ pub enum AnnotationSource {
 #[derive(Copy, Clone, Debug, HashStable)]
 pub struct DestructuredConstant<'tcx> {
     pub variant: Option<VariantIdx>,
-    pub fields: &'tcx [(ConstValue<'tcx>, Ty<'tcx>)],
+    pub fields: &'tcx [(ConstValue, Ty<'tcx>)],
 }

compiler/rustc_middle/src/query/erase.rs

@@ -153,8 +153,8 @@ impl EraseType for Result<mir::ConstAlloc<'_>, mir::interpret::ErrorHandled> {
     type Result = [u8; size_of::<Result<mir::ConstAlloc<'static>, mir::interpret::ErrorHandled>>()];
 }
 
-impl EraseType for Result<mir::ConstValue<'_>, mir::interpret::ErrorHandled> {
-    type Result = [u8; size_of::<Result<mir::ConstValue<'static>, mir::interpret::ErrorHandled>>()];
+impl EraseType for Result<mir::ConstValue, mir::interpret::ErrorHandled> {
+    type Result = [u8; size_of::<Result<mir::ConstValue, mir::interpret::ErrorHandled>>()];
 }
 
 impl EraseType for EvalToValTreeResult<'_> {
@@ -301,6 +301,7 @@ trivial! {
     rustc_middle::middle::resolve_bound_vars::ResolvedArg,
     rustc_middle::middle::stability::DeprecationEntry,
     rustc_middle::mir::ConstQualifs,
+    rustc_middle::mir::ConstValue,
     rustc_middle::mir::interpret::AllocId,
     rustc_middle::mir::interpret::CtfeProvenance,
     rustc_middle::mir::interpret::ErrorHandled,
@@ -362,7 +363,6 @@ tcx_lifetime! {
     rustc_middle::mir::Const,
     rustc_middle::mir::DestructuredConstant,
     rustc_middle::mir::ConstAlloc,
-    rustc_middle::mir::ConstValue,
     rustc_middle::mir::interpret::GlobalId,
     rustc_middle::mir::interpret::LitToConstInput,
     rustc_middle::mir::interpret::EvalStaticInitializerRawResult,

compiler/rustc_middle/src/query/mod.rs

@@ -1363,7 +1363,7 @@ rustc_queries! {
     }
 
     /// Converts a type-level constant value into a MIR constant value.
-    query valtree_to_const_val(key: ty::Value<'tcx>) -> mir::ConstValue<'tcx> {
+    query valtree_to_const_val(key: ty::Value<'tcx>) -> mir::ConstValue {
         desc { "converting type-level constant value to MIR constant value"}
     }
 
@@ -2152,9 +2152,6 @@ rustc_queries! {
         desc { |tcx| "collecting child items of module `{}`", tcx.def_path_str(def_id) }
         separate_provide_extern
     }
-    query extern_mod_stmt_cnum(def_id: LocalDefId) -> Option<CrateNum> {
-        desc { |tcx| "computing crate imported by `{}`", tcx.def_path_str(def_id) }
-    }
 
     /// Gets the number of definitions in a foreign crate.
     ///
@@ -2285,9 +2282,6 @@ rustc_queries! {
     query upvars_mentioned(def_id: DefId) -> Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>> {
         desc { |tcx| "collecting upvars mentioned in `{}`", tcx.def_path_str(def_id) }
     }
-    query maybe_unused_trait_imports(_: ()) -> &'tcx FxIndexSet<LocalDefId> {
-        desc { "fetching potentially unused trait imports" }
-    }
 
     /// All available crates in the graph, including those that should not be user-facing
     /// (such as private crates).

compiler/rustc_middle/src/ty/context.rs

@@ -5,7 +5,7 @@
 pub mod tls;
 
 use std::assert_matches::debug_assert_matches;
-use std::borrow::Borrow;
+use std::borrow::{Borrow, Cow};
 use std::cmp::Ordering;
 use std::env::VarError;
 use std::ffi::OsStr;
@@ -1625,7 +1625,11 @@ impl<'tcx> TyCtxt<'tcx> {
 
     /// Allocates a read-only byte or string literal for `mir::interpret` with alignment 1.
     /// Returns the same `AllocId` if called again with the same bytes.
-    pub fn allocate_bytes_dedup(self, bytes: &[u8], salt: usize) -> interpret::AllocId {
+    pub fn allocate_bytes_dedup<'a>(
+        self,
+        bytes: impl Into<Cow<'a, [u8]>>,
+        salt: usize,
+    ) -> interpret::AllocId {
         // Create an allocation that just contains these bytes.
         let alloc = interpret::Allocation::from_bytes_byte_aligned_immutable(bytes, ());
         let alloc = self.mk_const_alloc(alloc);
@@ -3373,6 +3377,11 @@ impl<'tcx> TyCtxt<'tcx> {
         self.resolutions(()).module_children.get(&def_id).map_or(&[], |v| &v[..])
     }
 
+    /// Return the crate imported by given use item.
+    pub fn extern_mod_stmt_cnum(self, def_id: LocalDefId) -> Option<CrateNum> {
+        self.resolutions(()).extern_crate_map.get(&def_id).copied()
+    }
+
     pub fn resolver_for_lowering(self) -> &'tcx Steal<(ty::ResolverAstLowering, Arc<ast::Crate>)> {
         self.resolver_for_lowering_raw(()).0
     }
@@ -3410,6 +3419,20 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn do_not_recommend_impl(self, def_id: DefId) -> bool {
         self.get_diagnostic_attr(def_id, sym::do_not_recommend).is_some()
     }
+
+    /// Whether this def is one of the special bin crate entrypoint functions that must have a
+    /// monomorphization and also not be internalized in the bin crate.
+    pub fn is_entrypoint(self, def_id: DefId) -> bool {
+        if self.is_lang_item(def_id, LangItem::Start) {
+            return true;
+        }
+        if let Some((entry_def_id, _)) = self.entry_fn(())
+            && entry_def_id == def_id
+        {
+            return true;
+        }
+        false
+    }
 }
 
 /// Parameter attributes that can only be determined by examining the body of a function instead
@@ -3428,10 +3451,6 @@ pub struct DeducedParamAttrs {
 }
 
 pub fn provide(providers: &mut Providers) {
-    providers.maybe_unused_trait_imports =
-        |tcx, ()| &tcx.resolutions(()).maybe_unused_trait_imports;
-    providers.extern_mod_stmt_cnum =
-        |tcx, id| tcx.resolutions(()).extern_crate_map.get(&id).cloned();
     providers.is_panic_runtime =
         |tcx, LocalCrate| contains_name(tcx.hir_krate_attrs(), sym::panic_runtime);
     providers.is_compiler_builtins =

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -4,6 +4,7 @@
 //! to help with the tedium.
 
 use std::fmt::{self, Debug};
+use std::marker::PhantomData;
 
 use rustc_abi::TyAndLayout;
 use rustc_hir::def::Namespace;
@@ -234,6 +235,7 @@ TrivialLiftImpls! {
     rustc_abi::ExternAbi,
     rustc_abi::Size,
     rustc_hir::Safety,
+    rustc_middle::mir::ConstValue,
     rustc_type_ir::BoundConstness,
     rustc_type_ir::PredicatePolarity,
     // tidy-alphabetical-end
@@ -250,7 +252,7 @@ TrivialTypeTraversalImpls! {
     crate::mir::BlockTailInfo,
     crate::mir::BorrowKind,
     crate::mir::CastKind,
-    crate::mir::ConstValue<'tcx>,
+    crate::mir::ConstValue,
     crate::mir::CoroutineSavedLocal,
     crate::mir::FakeReadCause,
     crate::mir::Local,
@@ -311,6 +313,13 @@ TrivialTypeTraversalAndLiftImpls! {
 ///////////////////////////////////////////////////////////////////////////
 // Lift implementations
 
+impl<'tcx> Lift<TyCtxt<'tcx>> for PhantomData<&()> {
+    type Lifted = PhantomData<&'tcx ()>;
+    fn lift_to_interner(self, _: TyCtxt<'tcx>) -> Option<Self::Lifted> {
+        Some(PhantomData)
+    }
+}
+
 impl<'tcx, T: Lift<TyCtxt<'tcx>>> Lift<TyCtxt<'tcx>> for Option<T> {
     type Lifted = Option<T::Lifted>;
     fn lift_to_interner(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {

compiler/rustc_mir_build/src/builder/expr/as_constant.rs

@@ -3,7 +3,7 @@
 use rustc_abi::Size;
 use rustc_ast as ast;
 use rustc_hir::LangItem;
-use rustc_middle::mir::interpret::{Allocation, CTFE_ALLOC_SALT, LitToConstInput, Scalar};
+use rustc_middle::mir::interpret::{CTFE_ALLOC_SALT, LitToConstInput, Scalar};
 use rustc_middle::mir::*;
 use rustc_middle::thir::*;
 use rustc_middle::ty::{
@@ -120,17 +120,18 @@ fn lit_to_mir_constant<'tcx>(tcx: TyCtxt<'tcx>, lit_input: LitToConstInput<'tcx>
 
     let value = match (lit, lit_ty.kind()) {
         (ast::LitKind::Str(s, _), ty::Ref(_, inner_ty, _)) if inner_ty.is_str() => {
-            let s = s.as_str();
-            let allocation = Allocation::from_bytes_byte_aligned_immutable(s.as_bytes(), ());
-            let allocation = tcx.mk_const_alloc(allocation);
-            ConstValue::Slice { data: allocation, meta: allocation.inner().size().bytes() }
+            let s = s.as_str().as_bytes();
+            let len = s.len();
+            let allocation = tcx.allocate_bytes_dedup(s, CTFE_ALLOC_SALT);
+            ConstValue::Slice { alloc_id: allocation, meta: len.try_into().unwrap() }
         }
-        (ast::LitKind::ByteStr(data, _), ty::Ref(_, inner_ty, _))
+        (ast::LitKind::ByteStr(byte_sym, _), ty::Ref(_, inner_ty, _))
             if matches!(inner_ty.kind(), ty::Slice(_)) =>
         {
-            let allocation = Allocation::from_bytes_byte_aligned_immutable(data.as_byte_str(), ());
-            let allocation = tcx.mk_const_alloc(allocation);
-            ConstValue::Slice { data: allocation, meta: allocation.inner().size().bytes() }
+            let data = byte_sym.as_byte_str();
+            let len = data.len();
+            let allocation = tcx.allocate_bytes_dedup(data, CTFE_ALLOC_SALT);
+            ConstValue::Slice { alloc_id: allocation, meta: len.try_into().unwrap() }
         }
         (ast::LitKind::ByteStr(byte_sym, _), ty::Ref(_, inner_ty, _)) if inner_ty.is_array() => {
             let id = tcx.allocate_bytes_dedup(byte_sym.as_byte_str(), CTFE_ALLOC_SALT);
@@ -138,10 +139,10 @@ fn lit_to_mir_constant<'tcx>(tcx: TyCtxt<'tcx>, lit_input: LitToConstInput<'tcx>
         }
         (ast::LitKind::CStr(byte_sym, _), ty::Ref(_, inner_ty, _)) if matches!(inner_ty.kind(), ty::Adt(def, _) if tcx.is_lang_item(def.did(), LangItem::CStr)) =>
         {
-            let allocation =
-                Allocation::from_bytes_byte_aligned_immutable(byte_sym.as_byte_str(), ());
-            let allocation = tcx.mk_const_alloc(allocation);
-            ConstValue::Slice { data: allocation, meta: allocation.inner().size().bytes() }
+            let data = byte_sym.as_byte_str();
+            let len = data.len();
+            let allocation = tcx.allocate_bytes_dedup(data, CTFE_ALLOC_SALT);
+            ConstValue::Slice { alloc_id: allocation, meta: len.try_into().unwrap() }
         }
         (ast::LitKind::Byte(n), ty::Uint(ty::UintTy::U8)) => {
             ConstValue::Scalar(Scalar::from_uint(n, Size::from_bytes(1)))

compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs

@@ -1,6 +1,6 @@
 //! See docs in `build/expr/mod.rs`.
 
-use rustc_abi::{BackendRepr, FieldIdx, Primitive};
+use rustc_abi::FieldIdx;
 use rustc_hir::lang_items::LangItem;
 use rustc_index::{Idx, IndexVec};
 use rustc_middle::bug;
@@ -9,7 +9,6 @@ use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::mir::*;
 use rustc_middle::thir::*;
 use rustc_middle::ty::cast::{CastTy, mir_cast_kind};
-use rustc_middle::ty::layout::IntegerExt;
 use rustc_middle::ty::util::IntTypeExt;
 use rustc_middle::ty::{self, Ty, UpvarArgs};
 use rustc_span::source_map::Spanned;
@@ -200,8 +199,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 {
                     let discr_ty = adt_def.repr().discr_type().to_ty(this.tcx);
                     let temp = unpack!(block = this.as_temp(block, scope, source, Mutability::Not));
-                    let layout =
-                        this.tcx.layout_of(this.typing_env().as_query_input(source_expr.ty));
                     let discr = this.temp(discr_ty, source_expr.span);
                     this.cfg.push_assign(
                         block,
@@ -209,80 +206,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         discr,
                         Rvalue::Discriminant(temp.into()),
                     );
-                    let (op, ty) = (Operand::Move(discr), discr_ty);
-
-                    if let BackendRepr::Scalar(scalar) = layout.unwrap().backend_repr
-                        && !scalar.is_always_valid(&this.tcx)
-                        && let Primitive::Int(int_width, _signed) = scalar.primitive()
-                    {
-                        let unsigned_ty = int_width.to_ty(this.tcx, false);
-                        let unsigned_place = this.temp(unsigned_ty, expr_span);
-                        this.cfg.push_assign(
-                            block,
-                            source_info,
-                            unsigned_place,
-                            Rvalue::Cast(CastKind::IntToInt, Operand::Copy(discr), unsigned_ty),
-                        );
-
-                        let bool_ty = this.tcx.types.bool;
-                        let range = scalar.valid_range(&this.tcx);
-                        let merge_op =
-                            if range.start <= range.end { BinOp::BitAnd } else { BinOp::BitOr };
-
-                        let mut comparer = |range: u128, bin_op: BinOp| -> Place<'tcx> {
-                            // We can use `ty::TypingEnv::fully_monomorphized()` here
-                            // as we only need it to compute the layout of a primitive.
-                            let range_val = Const::from_bits(
-                                this.tcx,
-                                range,
-                                ty::TypingEnv::fully_monomorphized(),
-                                unsigned_ty,
-                            );
-                            let lit_op = this.literal_operand(expr.span, range_val);
-                            let is_bin_op = this.temp(bool_ty, expr_span);
-                            this.cfg.push_assign(
-                                block,
-                                source_info,
-                                is_bin_op,
-                                Rvalue::BinaryOp(
-                                    bin_op,
-                                    Box::new((Operand::Copy(unsigned_place), lit_op)),
-                                ),
-                            );
-                            is_bin_op
-                        };
-                        let assert_place = if range.start == 0 {
-                            comparer(range.end, BinOp::Le)
-                        } else {
-                            let start_place = comparer(range.start, BinOp::Ge);
-                            let end_place = comparer(range.end, BinOp::Le);
-                            let merge_place = this.temp(bool_ty, expr_span);
-                            this.cfg.push_assign(
-                                block,
-                                source_info,
-                                merge_place,
-                                Rvalue::BinaryOp(
-                                    merge_op,
-                                    Box::new((
-                                        Operand::Move(start_place),
-                                        Operand::Move(end_place),
-                                    )),
-                                ),
-                            );
-                            merge_place
-                        };
-                        this.cfg.push(
-                            block,
-                            Statement::new(
-                                source_info,
-                                StatementKind::Intrinsic(Box::new(NonDivergingIntrinsic::Assume(
-                                    Operand::Move(assert_place),
-                                ))),
-                            ),
-                        );
-                    }
-
-                    (op, ty)
+                    (Operand::Move(discr), discr_ty)
                 } else {
                     let ty = source_expr.ty;
                     let source = unpack!(

compiler/rustc_mir_build/src/builder/mod.rs

@@ -1045,11 +1045,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     }
 }
 
-fn parse_float_into_constval<'tcx>(
-    num: Symbol,
-    float_ty: ty::FloatTy,
-    neg: bool,
-) -> Option<ConstValue<'tcx>> {
+fn parse_float_into_constval(num: Symbol, float_ty: ty::FloatTy, neg: bool) -> Option<ConstValue> {
     parse_float_into_scalar(num, float_ty, neg).map(|s| ConstValue::Scalar(s.into()))
 }
 

compiler/rustc_mir_transform/src/coverage/spans.rs

@@ -1,7 +1,8 @@
 use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::mir;
 use rustc_middle::ty::TyCtxt;
-use rustc_span::{DesugaringKind, ExpnKind, MacroKind, Span};
+use rustc_span::source_map::SourceMap;
+use rustc_span::{BytePos, DesugaringKind, ExpnKind, MacroKind, Span};
 use tracing::instrument;
 
 use crate::coverage::graph::{BasicCoverageBlock, CoverageGraph};
@@ -83,8 +84,18 @@ pub(super) fn extract_refined_covspans<'tcx>(
     // Discard any span that overlaps with a hole.
     discard_spans_overlapping_holes(&mut covspans, &holes);
 
-    // Perform more refinement steps after holes have been dealt with.
+    // Discard spans that overlap in unwanted ways.
     let mut covspans = remove_unwanted_overlapping_spans(covspans);
+
+    // For all empty spans, either enlarge them to be non-empty, or discard them.
+    let source_map = tcx.sess.source_map();
+    covspans.retain_mut(|covspan| {
+        let Some(span) = ensure_non_empty_span(source_map, covspan.span) else { return false };
+        covspan.span = span;
+        true
+    });
+
+    // Merge covspans that can be merged.
     covspans.dedup_by(|b, a| a.merge_if_eligible(b));
 
     code_mappings.extend(covspans.into_iter().map(|Covspan { span, bcb }| {
@@ -230,3 +241,26 @@ fn compare_spans(a: Span, b: Span) -> std::cmp::Ordering {
         // - Both have the same start and span A extends further right
         .then_with(|| Ord::cmp(&a.hi(), &b.hi()).reverse())
 }
+
+fn ensure_non_empty_span(source_map: &SourceMap, span: Span) -> Option<Span> {
+    if !span.is_empty() {
+        return Some(span);
+    }
+
+    // The span is empty, so try to enlarge it to cover an adjacent '{' or '}'.
+    source_map
+        .span_to_source(span, |src, start, end| try {
+            // Adjusting span endpoints by `BytePos(1)` is normally a bug,
+            // but in this case we have specifically checked that the character
+            // we're skipping over is one of two specific ASCII characters, so
+            // adjusting by exactly 1 byte is correct.
+            if src.as_bytes().get(end).copied() == Some(b'{') {
+                Some(span.with_hi(span.hi() + BytePos(1)))
+            } else if start > 0 && src.as_bytes()[start - 1] == b'}' {
+                Some(span.with_lo(span.lo() - BytePos(1)))
+            } else {
+                None
+            }
+        })
+        .ok()?
+}

compiler/rustc_mir_transform/src/gvn.rs

@@ -1542,7 +1542,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
 fn op_to_prop_const<'tcx>(
     ecx: &mut InterpCx<'tcx, DummyMachine>,
     op: &OpTy<'tcx>,
-) -> Option<ConstValue<'tcx>> {
+) -> Option<ConstValue> {
     // Do not attempt to propagate unsized locals.
     if op.layout.is_unsized() {
         return None;

compiler/rustc_mir_transform/src/impossible_predicates.rs

@@ -27,7 +27,7 @@
 //! it's usually never invoked in this way.
 
 use rustc_middle::mir::{Body, START_BLOCK, TerminatorKind};
-use rustc_middle::ty::{TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{TyCtxt, TypeFlags, TypeVisitableExt};
 use rustc_trait_selection::traits;
 use tracing::trace;
 
@@ -36,14 +36,23 @@ use crate::pass_manager::MirPass;
 pub(crate) struct ImpossiblePredicates;
 
 impl<'tcx> MirPass<'tcx> for ImpossiblePredicates {
+    #[tracing::instrument(level = "trace", skip(self, tcx, body))]
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-        let predicates = tcx
-            .predicates_of(body.source.def_id())
-            .predicates
-            .iter()
-            .filter_map(|(p, _)| if p.is_global() { Some(*p) } else { None });
-        if traits::impossible_predicates(tcx, traits::elaborate(tcx, predicates).collect()) {
-            trace!("found unsatisfiable predicates for {:?}", body.source);
+        tracing::trace!(def_id = ?body.source.def_id());
+        let predicates = tcx.predicates_of(body.source.def_id()).instantiate_identity(tcx);
+        tracing::trace!(?predicates);
+        let predicates = predicates.predicates.into_iter().filter(|p| {
+            !p.has_type_flags(
+                // Only consider global clauses to simplify.
+                TypeFlags::HAS_FREE_LOCAL_NAMES
+                // Clauses that refer to unevaluated constants as they cause cycles.
+                | TypeFlags::HAS_CT_PROJECTION,
+            )
+        });
+        let predicates: Vec<_> = traits::elaborate(tcx, predicates).collect();
+        tracing::trace!(?predicates);
+        if predicates.references_error() || traits::impossible_predicates(tcx, predicates) {
+            trace!("found unsatisfiable predicates");
             // Clear the body to only contain a single `unreachable` statement.
             let bbs = body.basic_blocks.as_mut();
             bbs.raw.truncate(1);

compiler/rustc_mir_transform/src/unreachable_prop.rs

@@ -75,7 +75,7 @@ fn remove_successors_from_switch<'tcx>(
     let is_unreachable = |bb| unreachable_blocks.contains(&bb);
 
     // If there are multiple targets, we want to keep information about reachability for codegen.
-    // For example (see tests/codegen/match-optimizes-away.rs)
+    // For example (see tests/codegen-llvm/match-optimizes-away.rs)
     //
     // pub enum Two { A, B }
     // pub fn identity(x: Two) -> Two {

compiler/rustc_monomorphize/src/collector.rs

@@ -659,10 +659,7 @@ impl<'a, 'tcx> MirUsedCollector<'a, 'tcx> {
     }
 
     /// Evaluates a *not yet monomorphized* constant.
-    fn eval_constant(
-        &mut self,
-        constant: &mir::ConstOperand<'tcx>,
-    ) -> Option<mir::ConstValue<'tcx>> {
+    fn eval_constant(&mut self, constant: &mir::ConstOperand<'tcx>) -> Option<mir::ConstValue> {
         let const_ = self.monomorphize(constant.const_);
         // Evaluate the constant. This makes const eval failure a collection-time error (rather than
         // a codegen-time error). rustc stops after collection if there was an error, so this
@@ -1355,19 +1352,15 @@ fn visit_mentioned_item<'tcx>(
 #[instrument(skip(tcx, output), level = "debug")]
 fn collect_const_value<'tcx>(
     tcx: TyCtxt<'tcx>,
-    value: mir::ConstValue<'tcx>,
+    value: mir::ConstValue,
     output: &mut MonoItems<'tcx>,
 ) {
     match value {
         mir::ConstValue::Scalar(Scalar::Ptr(ptr, _size)) => {
             collect_alloc(tcx, ptr.provenance.alloc_id(), output)
         }
-        mir::ConstValue::Indirect { alloc_id, .. } => collect_alloc(tcx, alloc_id, output),
-        mir::ConstValue::Slice { data, meta: _ } => {
-            for &prov in data.inner().provenance().ptrs().values() {
-                collect_alloc(tcx, prov.alloc_id(), output);
-            }
-        }
+        mir::ConstValue::Indirect { alloc_id, .. }
+        | mir::ConstValue::Slice { alloc_id, meta: _ } => collect_alloc(tcx, alloc_id, output),
         _ => {}
     }
 }
@@ -1582,6 +1575,15 @@ impl<'v> RootCollector<'_, 'v> {
             return;
         };
 
+        let main_instance = Instance::mono(self.tcx, main_def_id);
+        if self.tcx.should_codegen_locally(main_instance) {
+            self.output.push(create_fn_mono_item(
+                self.tcx,
+                main_instance,
+                self.tcx.def_span(main_def_id),
+            ));
+        }
+
         let Some(start_def_id) = self.tcx.lang_items().start_fn() else {
             self.tcx.dcx().emit_fatal(errors::StartNotFound);
         };

compiler/rustc_monomorphize/src/partitioning.rs

@@ -223,11 +223,7 @@ where
         // So even if its mode is LocalCopy, we need to treat it like a root.
         match mono_item.instantiation_mode(cx.tcx) {
             InstantiationMode::GloballyShared { .. } => {}
-            InstantiationMode::LocalCopy => {
-                if !cx.tcx.is_lang_item(mono_item.def_id(), LangItem::Start) {
-                    continue;
-                }
-            }
+            InstantiationMode::LocalCopy => continue,
         }
 
         let characteristic_def_id = characteristic_def_id_of_mono_item(cx.tcx, mono_item);
@@ -821,10 +817,9 @@ fn mono_item_visibility<'tcx>(
         | InstanceKind::FnPtrAddrShim(..) => return Visibility::Hidden,
     };
 
-    // The `start_fn` lang item is actually a monomorphized instance of a
-    // function in the standard library, used for the `main` function. We don't
-    // want to export it so we tag it with `Hidden` visibility but this symbol
-    // is only referenced from the actual `main` symbol which we unfortunately
+    // Both the `start_fn` lang item and `main` itself should not be exported,
+    // so we give them with `Hidden` visibility but these symbols are
+    // only referenced from the actual `main` symbol which we unfortunately
     // don't know anything about during partitioning/collection. As a result we
     // forcibly keep this symbol out of the `internalization_candidates` set.
     //
@@ -834,7 +829,7 @@ fn mono_item_visibility<'tcx>(
     //        from the `main` symbol we'll generate later.
     //
     //        This may be fixable with a new `InstanceKind` perhaps? Unsure!
-    if tcx.is_lang_item(def_id, LangItem::Start) {
+    if tcx.is_entrypoint(def_id) {
         *can_be_internalized = false;
         return Visibility::Hidden;
     }

compiler/rustc_parse/src/lexer/diagnostics.rs

@@ -126,23 +126,29 @@ pub(super) fn report_suspicious_mismatch_block(
     }
 }
 
-pub(crate) fn make_unclosed_delims_error(
-    unmatched: UnmatchedDelim,
-    psess: &ParseSess,
-) -> Option<Diag<'_>> {
-    // `None` here means an `Eof` was found. We already emit those errors elsewhere, we add them to
-    // `unmatched_delims` only for error recovery in the `Parser`.
-    let found_delim = unmatched.found_delim?;
-    let mut spans = vec![unmatched.found_span];
-    if let Some(sp) = unmatched.unclosed_span {
-        spans.push(sp);
-    };
-    let err = psess.dcx().create_err(MismatchedClosingDelimiter {
-        spans,
-        delimiter: pprust::token_kind_to_string(&found_delim.as_close_token_kind()).to_string(),
-        unmatched: unmatched.found_span,
-        opening_candidate: unmatched.candidate_span,
-        unclosed: unmatched.unclosed_span,
-    });
-    Some(err)
+pub(crate) fn make_errors_for_mismatched_closing_delims<'psess>(
+    unmatcheds: &[UnmatchedDelim],
+    psess: &'psess ParseSess,
+) -> Vec<Diag<'psess>> {
+    unmatcheds
+        .iter()
+        .filter_map(|unmatched| {
+            // `None` here means an `Eof` was found. We already emit those errors elsewhere, we add them to
+            // `unmatched_delims` only for error recovery in the `Parser`.
+            let found_delim = unmatched.found_delim?;
+            let mut spans = vec![unmatched.found_span];
+            if let Some(sp) = unmatched.unclosed_span {
+                spans.push(sp);
+            };
+            let err = psess.dcx().create_err(MismatchedClosingDelimiter {
+                spans,
+                delimiter: pprust::token_kind_to_string(&found_delim.as_close_token_kind())
+                    .to_string(),
+                unmatched: unmatched.found_span,
+                opening_candidate: unmatched.candidate_span,
+                unclosed: unmatched.unclosed_span,
+            });
+            Some(err)
+        })
+        .collect()
 }

compiler/rustc_parse/src/lexer/mod.rs

@@ -1,4 +1,4 @@
-use diagnostics::make_unclosed_delims_error;
+use diagnostics::make_errors_for_mismatched_closing_delims;
 use rustc_ast::ast::{self, AttrStyle};
 use rustc_ast::token::{self, CommentKind, Delimiter, IdentIsRaw, Token, TokenKind};
 use rustc_ast::tokenstream::TokenStream;
@@ -71,27 +71,23 @@ pub(crate) fn lex_token_trees<'psess, 'src>(
     };
     let res = lexer.lex_token_trees(/* is_delimited */ false);
 
-    let mut unmatched_delims: Vec<_> = lexer
-        .diag_info
-        .unmatched_delims
-        .into_iter()
-        .filter_map(|unmatched_delim| make_unclosed_delims_error(unmatched_delim, psess))
-        .collect();
+    let mut unmatched_closing_delims: Vec<_> =
+        make_errors_for_mismatched_closing_delims(&lexer.diag_info.unmatched_delims, psess);
 
     match res {
         Ok((_open_spacing, stream)) => {
-            if unmatched_delims.is_empty() {
+            if unmatched_closing_delims.is_empty() {
                 Ok(stream)
             } else {
                 // Return error if there are unmatched delimiters or unclosed delimiters.
-                Err(unmatched_delims)
+                Err(unmatched_closing_delims)
             }
         }
         Err(errs) => {
             // We emit delimiter mismatch errors first, then emit the unclosing delimiter mismatch
             // because the delimiter mismatch is more likely to be the root cause of error
-            unmatched_delims.extend(errs);
-            Err(unmatched_delims)
+            unmatched_closing_delims.extend(errs);
+            Err(unmatched_closing_delims)
         }
     }
 }

compiler/rustc_parse/src/lexer/tokentrees.rs

@@ -51,45 +51,6 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
         }
     }
 
-    fn eof_err(&mut self) -> Diag<'psess> {
-        let msg = "this file contains an unclosed delimiter";
-        let mut err = self.dcx().struct_span_err(self.token.span, msg);
-
-        let unclosed_delimiter_show_limit = 5;
-        let len = usize::min(unclosed_delimiter_show_limit, self.diag_info.open_delimiters.len());
-        for &(_, span) in &self.diag_info.open_delimiters[..len] {
-            err.span_label(span, "unclosed delimiter");
-            self.diag_info.unmatched_delims.push(UnmatchedDelim {
-                found_delim: None,
-                found_span: self.token.span,
-                unclosed_span: Some(span),
-                candidate_span: None,
-            });
-        }
-
-        if let Some((_, span)) = self.diag_info.open_delimiters.get(unclosed_delimiter_show_limit)
-            && self.diag_info.open_delimiters.len() >= unclosed_delimiter_show_limit + 2
-        {
-            err.span_label(
-                *span,
-                format!(
-                    "another {} unclosed delimiters begin from here",
-                    self.diag_info.open_delimiters.len() - unclosed_delimiter_show_limit
-                ),
-            );
-        }
-
-        if let Some((delim, _)) = self.diag_info.open_delimiters.last() {
-            report_suspicious_mismatch_block(
-                &mut err,
-                &self.diag_info,
-                self.psess.source_map(),
-                *delim,
-            )
-        }
-        err
-    }
-
     fn lex_token_tree_open_delim(
         &mut self,
         open_delim: Delimiter,
@@ -206,13 +167,7 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
             } else if let Some(glued) = self.token.glue(&next_tok) {
                 self.token = glued;
             } else {
-                let this_spacing = if next_tok.is_punct() {
-                    Spacing::Joint
-                } else if next_tok == token::Eof {
-                    Spacing::Alone
-                } else {
-                    Spacing::JointHidden
-                };
+                let this_spacing = self.calculate_spacing(&next_tok);
                 break (this_spacing, next_tok);
             }
         };
@@ -223,23 +178,64 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
     // Cut-down version of `bump` used when the token kind is known in advance.
     fn bump_minimal(&mut self) -> Spacing {
         let (next_tok, is_next_tok_preceded_by_whitespace) = self.next_token_from_cursor();
-
         let this_spacing = if is_next_tok_preceded_by_whitespace {
             Spacing::Alone
         } else {
-            if next_tok.is_punct() {
-                Spacing::Joint
-            } else if next_tok == token::Eof {
-                Spacing::Alone
-            } else {
-                Spacing::JointHidden
-            }
+            self.calculate_spacing(&next_tok)
         };
-
         self.token = next_tok;
         this_spacing
     }
 
+    fn calculate_spacing(&self, next_tok: &Token) -> Spacing {
+        if next_tok.is_punct() {
+            Spacing::Joint
+        } else if *next_tok == token::Eof {
+            Spacing::Alone
+        } else {
+            Spacing::JointHidden
+        }
+    }
+
+    fn eof_err(&mut self) -> Diag<'psess> {
+        const UNCLOSED_DELIMITER_SHOW_LIMIT: usize = 5;
+        let msg = "this file contains an unclosed delimiter";
+        let mut err = self.dcx().struct_span_err(self.token.span, msg);
+
+        let len = usize::min(UNCLOSED_DELIMITER_SHOW_LIMIT, self.diag_info.open_delimiters.len());
+        for &(_, span) in &self.diag_info.open_delimiters[..len] {
+            err.span_label(span, "unclosed delimiter");
+            self.diag_info.unmatched_delims.push(UnmatchedDelim {
+                found_delim: None,
+                found_span: self.token.span,
+                unclosed_span: Some(span),
+                candidate_span: None,
+            });
+        }
+
+        if let Some((_, span)) = self.diag_info.open_delimiters.get(UNCLOSED_DELIMITER_SHOW_LIMIT)
+            && self.diag_info.open_delimiters.len() >= UNCLOSED_DELIMITER_SHOW_LIMIT + 2
+        {
+            err.span_label(
+                *span,
+                format!(
+                    "another {} unclosed delimiters begin from here",
+                    self.diag_info.open_delimiters.len() - UNCLOSED_DELIMITER_SHOW_LIMIT
+                ),
+            );
+        }
+
+        if let Some((delim, _)) = self.diag_info.open_delimiters.last() {
+            report_suspicious_mismatch_block(
+                &mut err,
+                &self.diag_info,
+                self.psess.source_map(),
+                *delim,
+            )
+        }
+        err
+    }
+
     fn close_delim_err(&mut self, delim: Delimiter) -> Diag<'psess> {
         // An unexpected closing delimiter (i.e., there is no matching opening delimiter).
         let token_str = token_to_string(&self.token);

compiler/rustc_parse/src/validate_attr.rs

@@ -285,6 +285,9 @@ pub fn check_builtin_meta_item(
                 | sym::rustc_do_not_implement_via_object
                 | sym::rustc_coinductive
                 | sym::const_trait
+                | sym::stable
+                | sym::unstable
+                | sym::rustc_allowed_through_unstable_modules
                 | sym::rustc_specialization_trait
                 | sym::rustc_unsafe_specialization_marker
                 | sym::rustc_allow_incoherent_impl
@@ -303,6 +306,8 @@ pub fn check_builtin_meta_item(
                 | sym::cold
                 | sym::target_feature
                 | sym::rustc_allow_const_fn_unstable
+                | sym::macro_use
+                | sym::macro_escape
                 | sym::naked
                 | sym::no_mangle
                 | sym::non_exhaustive

compiler/rustc_passes/src/check_attr.rs

@@ -227,6 +227,12 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 Attribute::Parsed(AttributeKind::LinkSection { span: attr_span, .. }) => {
                     self.check_link_section(hir_id, *attr_span, span, target)
                 }
+                Attribute::Parsed(AttributeKind::MacroUse { span, .. }) => {
+                    self.check_macro_use(hir_id, sym::macro_use, *span, target)
+                }
+                Attribute::Parsed(AttributeKind::MacroEscape(span)) => {
+                    self.check_macro_use(hir_id, sym::macro_escape, *span, target)
+                }
                 Attribute::Parsed(AttributeKind::Naked(attr_span)) => {
                     self.check_naked(hir_id, *attr_span, span, target)
                 }
@@ -362,9 +368,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         [sym::ffi_pure, ..] => self.check_ffi_pure(attr.span(), attrs, target),
                         [sym::ffi_const, ..] => self.check_ffi_const(attr.span(), target),
                         [sym::link, ..] => self.check_link(hir_id, attr, span, target),
-                        [sym::macro_use, ..] | [sym::macro_escape, ..] => {
-                            self.check_macro_use(hir_id, attr, target)
-                        }
                         [sym::path, ..] => self.check_generic_attr_unparsed(hir_id, attr, target, Target::Mod),
                         [sym::macro_export, ..] => self.check_macro_export(hir_id, attr, target),
                         [sym::should_panic, ..] => {
@@ -1255,7 +1258,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             return;
         }
 
-        if self.tcx.extern_mod_stmt_cnum(hir_id.owner).is_none() {
+        if self.tcx.extern_mod_stmt_cnum(hir_id.owner.def_id).is_none() {
             self.tcx.emit_node_span_lint(
                 INVALID_DOC_ATTRIBUTES,
                 hir_id,
@@ -2411,17 +2414,14 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         }
     }
 
-    fn check_macro_use(&self, hir_id: HirId, attr: &Attribute, target: Target) {
-        let Some(name) = attr.name() else {
-            return;
-        };
+    fn check_macro_use(&self, hir_id: HirId, name: Symbol, attr_span: Span, target: Target) {
         match target {
             Target::ExternCrate | Target::Mod => {}
             _ => {
                 self.tcx.emit_node_span_lint(
                     UNUSED_ATTRIBUTES,
                     hir_id,
-                    attr.span(),
+                    attr_span,
                     errors::MacroUse { name },
                 );
             }
@@ -2474,7 +2474,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         // Warn on useless empty attributes.
         // FIXME(jdonszelmann): this lint should be moved to attribute parsing, see `AcceptContext::warn_empty_attribute`
         let note = if attr.has_any_name(&[
-            sym::macro_use,
             sym::allow,
             sym::expect,
             sym::warn,

compiler/rustc_privacy/src/lib.rs

@@ -26,7 +26,7 @@ use rustc_errors::{MultiSpan, listify};
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId, LocalDefId, LocalModDefId};
 use rustc_hir::intravisit::{self, InferKind, Visitor};
-use rustc_hir::{AmbigArg, ForeignItemKind, ItemId, ItemKind, PatKind};
+use rustc_hir::{AmbigArg, ForeignItemId, ItemId, PatKind};
 use rustc_middle::middle::privacy::{EffectiveVisibilities, EffectiveVisibility, Level};
 use rustc_middle::query::Providers;
 use rustc_middle::ty::print::PrintTraitRefExt as _;
@@ -599,18 +599,13 @@ impl<'tcx> EmbargoVisitor<'tcx> {
 
             DefKind::Struct | DefKind::Union => {
                 // While structs and unions have type privacy, their fields do not.
-                let item = self.tcx.hir_expect_item(def_id);
-                if let hir::ItemKind::Struct(_, _, ref struct_def)
-                | hir::ItemKind::Union(_, _, ref struct_def) = item.kind
-                {
-                    for field in struct_def.fields() {
-                        let field_vis = self.tcx.local_visibility(field.def_id);
-                        if field_vis.is_accessible_from(module, self.tcx) {
-                            self.reach(field.def_id, macro_ev).ty();
-                        }
+                let struct_def = self.tcx.adt_def(def_id);
+                for field in struct_def.non_enum_variant().fields.iter() {
+                    let def_id = field.did.expect_local();
+                    let field_vis = self.tcx.local_visibility(def_id);
+                    if field_vis.is_accessible_from(module, self.tcx) {
+                        self.reach(def_id, macro_ev).ty();
                     }
-                } else {
-                    bug!("item {:?} with DefKind {:?}", item, def_kind);
                 }
             }
 
@@ -1644,66 +1639,29 @@ impl<'tcx> PrivateItemsInPublicInterfacesChecker<'_, 'tcx> {
                 self.check(def_id, item_visibility, effective_vis).generics().predicates();
             }
             DefKind::Enum => {
-                let item = tcx.hir_item(id);
-                if let hir::ItemKind::Enum(_, _, ref def) = item.kind {
-                    self.check_unnameable(item.owner_id.def_id, effective_vis);
+                self.check_unnameable(def_id, effective_vis);
+                self.check(def_id, item_visibility, effective_vis).generics().predicates();
 
-                    self.check(item.owner_id.def_id, item_visibility, effective_vis)
-                        .generics()
-                        .predicates();
-
-                    for variant in def.variants {
-                        for field in variant.data.fields() {
-                            self.check(field.def_id, item_visibility, effective_vis).ty();
-                        }
-                    }
-                }
-            }
-            // Subitems of foreign modules have their own publicity.
-            DefKind::ForeignMod => {
-                let item = tcx.hir_item(id);
-                if let hir::ItemKind::ForeignMod { items, .. } = item.kind {
-                    for &foreign_item in items {
-                        let foreign_item = tcx.hir_foreign_item(foreign_item);
-
-                        let ev = self.get(foreign_item.owner_id.def_id);
-                        let vis = tcx.local_visibility(foreign_item.owner_id.def_id);
-
-                        if let ForeignItemKind::Type = foreign_item.kind {
-                            self.check_unnameable(foreign_item.owner_id.def_id, ev);
-                        }
-
-                        self.check(foreign_item.owner_id.def_id, vis, ev)
-                            .generics()
-                            .predicates()
-                            .ty();
-                    }
+                let adt = tcx.adt_def(id.owner_id);
+                for field in adt.all_fields() {
+                    self.check(field.did.expect_local(), item_visibility, effective_vis).ty();
                 }
             }
             // Subitems of structs and unions have their own publicity.
             DefKind::Struct | DefKind::Union => {
-                let item = tcx.hir_item(id);
-                if let hir::ItemKind::Struct(_, _, ref struct_def)
-                | hir::ItemKind::Union(_, _, ref struct_def) = item.kind
-                {
-                    self.check_unnameable(item.owner_id.def_id, effective_vis);
-                    self.check(item.owner_id.def_id, item_visibility, effective_vis)
-                        .generics()
-                        .predicates();
+                self.check_unnameable(def_id, effective_vis);
+                self.check(def_id, item_visibility, effective_vis).generics().predicates();
 
-                    for field in struct_def.fields() {
-                        let field_visibility = tcx.local_visibility(field.def_id);
-                        let field_ev = self.get(field.def_id);
+                let adt = tcx.adt_def(id.owner_id);
+                for field in adt.all_fields() {
+                    let visibility = min(item_visibility, field.vis.expect_local(), tcx);
+                    let field_ev = self.get(field.did.expect_local());
 
-                        self.check(
-                            field.def_id,
-                            min(item_visibility, field_visibility, tcx),
-                            field_ev,
-                        )
-                        .ty();
-                    }
+                    self.check(field.did.expect_local(), visibility, field_ev).ty();
                 }
             }
+            // Subitems of foreign modules have their own publicity.
+            DefKind::ForeignMod => {}
             // An inherent impl is public when its type is public
             // Subitems of inherent impls have their own publicity.
             // A trait impl is public when both its type and its trait are public
@@ -1763,6 +1721,19 @@ impl<'tcx> PrivateItemsInPublicInterfacesChecker<'_, 'tcx> {
             _ => {}
         }
     }
+
+    fn check_foreign_item(&mut self, id: ForeignItemId) {
+        let tcx = self.tcx;
+        let def_id = id.owner_id.def_id;
+        let item_visibility = tcx.local_visibility(def_id);
+        let effective_vis = self.get(def_id);
+
+        if let DefKind::ForeignTy = self.tcx.def_kind(def_id) {
+            self.check_unnameable(def_id, effective_vis);
+        }
+
+        self.check(def_id, item_visibility, effective_vis).generics().predicates().ty();
+    }
 }
 
 pub fn provide(providers: &mut Providers) {
@@ -1791,20 +1762,13 @@ fn check_mod_privacy(tcx: TyCtxt<'_>, module_def_id: LocalModDefId) {
         if let Some(body_id) = tcx.hir_maybe_body_owned_by(def_id) {
             visitor.visit_nested_body(body_id.id());
         }
-    }
 
-    for id in module.free_items() {
-        if let ItemKind::Impl(i) = tcx.hir_item(id).kind {
-            if let Some(item) = i.of_trait {
-                let trait_ref = tcx.impl_trait_ref(id.owner_id.def_id).unwrap();
-                let trait_ref = trait_ref.instantiate_identity();
-                visitor.span = item.path.span;
-                let _ = visitor.visit_def_id(
-                    trait_ref.def_id,
-                    "trait",
-                    &trait_ref.print_only_trait_path(),
-                );
-            }
+        if let DefKind::Impl { of_trait: true } = tcx.def_kind(def_id) {
+            let trait_ref = tcx.impl_trait_ref(def_id).unwrap();
+            let trait_ref = trait_ref.instantiate_identity();
+            visitor.span = tcx.hir_expect_item(def_id).expect_impl().of_trait.unwrap().path.span;
+            let _ =
+                visitor.visit_def_id(trait_ref.def_id, "trait", &trait_ref.print_only_trait_path());
         }
     }
 }
@@ -1895,7 +1859,11 @@ fn check_private_in_public(tcx: TyCtxt<'_>, (): ()) {
     // Check for private types in public interfaces.
     let mut checker = PrivateItemsInPublicInterfacesChecker { tcx, effective_visibilities };
 
-    for id in tcx.hir_free_items() {
+    let crate_items = tcx.hir_crate_items(());
+    for id in crate_items.free_items() {
         checker.check_item(id);
     }
+    for id in crate_items.foreign_items() {
+        checker.check_foreign_item(id);
+    }
 }